If you own an iPhone, an iPad or almost any other modern Apple device, sooner or later you're likely to end up with an Apple ID. This essentially consists of a single login, your Apple ID - usually your name followed by iCloud.com, me.com, or mac.com - and a password.

An Apple ID is used for a wide range of services, such as iCloud, Find My iPhone, iTunes Match and Apple Music, as well as make purchases from iTunes and download Podcasts. In this article we explain how, and offer our simple tips for managing an Apple ID account.

Read next: How to check Apple ID balance and How to change Apple ID

What's an Apple ID?

An Apple ID is your passport into the ever-expanding Apple universe, and it takes the form of an email address and a password.

You'll need an Apple ID for everything from booking an appointment at the local Apple Store's Genius Bar, to making a FaceTime call, to setting up Apple Pay, to buying music, movies and apps. An Apple ID is also used to access your iCloud data and services, which includes tools such as iMessage, email, Reminders, Notes, Calendars, Photos storage, and so on.

More than this, however, is the fact that the Apple ID links your Apple devices or computers to each other, and to you. By logging in to Apple hardware with your Apple ID, you're telling Apple that it belongs to you, and that your shared data, apps and services can be made accessible on it.

It's possible to use a Mac or iOS device without an Apple ID but it would be a significantly diminished experience. For example, without an Apple ID you can't log into the App Store, so won't be able to download new apps on your iPhone, iPad or iPod touch.

In fact, if you own anything Apple then the chances are you've got an Apple ID already. (If not, see How to create an Apple ID.) But next you'll be wondering what you can use it for.

Signing in with an Apple ID

Actually signing in with the Apple ID you created is simple.

Signing into Apple ID on a Mac

iTunes: Click the Sign In link at the top right of the app window.

App Store: Click the Sign In entry under the Quick Links listing at the right of the window.

iCloud: Open System Preferences, click the iCloud icon, and then provide your login details.

iBooks: To read purchases click the Store menu entry, then Authorise This Computer. To sign in to purchase books, open the iBooks Store (click the Store button at the top left if viewing your library), then click the Sign In entry under the Quick Links listing at the right of the program window.

How to use an Apple ID account: iCloud

To activate iCloud on a Mac you'll need to open System Preferences, then click the iCloud icon

Signing into Apple ID on an iPhone/iPad/iPod touch

iTunes Store, App Store: Scroll to the bottom of the listing and click the Sign In button.

iBooks: You'll be prompted to login as soon as you start the app. If you opt not to, you'll be prompted to sign in should you attempt to make a purchase in the store or view your existing purchases.

iCloud: When setting up your iOS device you'll be prompted to login to iCloud but should you wish to do so later, open the Settings app and click the iCloud link.

Using two (or more) Apple IDs

Although creating an Apple ID also creates an iCloud account, Apple lets you use two separate Apple IDs concurrently - one just for accessing iCloud, and one for everything else, such as purchasing apps, music, movies and iBooks.

This can be wise because sometimes your main Apple ID used for purchasing can be locked because of fraud. Additionally, some people just don't like having a credit card linked to their iCloud account.

There's a very important note here: Apple does not let you merge two (or more) Apple IDs into a single account, or transfer purchases or data between Apple IDs. Additionally, once an Apple ID is logged into iTunes Store on a Mac or iOS device, you can't log in with a different Apple ID for a 90-day period. (You can luckily add multiple Apple IDs to an Apple TV so your family can share that device without the 90 day limitation.)

In other words, Apple is pretty keen for you to use a single Apple ID. It's certainly the least problematic option.

However, when setting up an iOS device you'll be offered the option of inputting two different Apple IDs - one for iCloud, and one for iTunes (see screenshot below) - and on a Mac you can enter different Apple IDs within iTunes, the Mac App Store, iBooks, and the iCloud configuration panel within System Preferences.

How to use an Apple ID account

Apple lets you use two Apple IDs on your iOS device, but frowns upon the practice

Family Sharing, and sharing an Apple ID

Once upon a time some people created an Apple ID and then allowed other family members or friends to use it to log into their own device. Thus, an app could be bought once and used on multiple devices, as could music and movies.

Mums and dads also shared their Apple ID with their children, who were too young to have a payment card on their account in order to make in-app purchases.

Sharing in this way never worked satisfactorily. Unwanted data synced across the shared devices, such as iMessages, but in any case it's become somewhat redundant since Apple introduced Family Sharing. This lets up to six separate Apple IDs share apps and iTunes purchases with no strings attached.

As its name suggests Family Sharing really is built for families. For example, it creates a shared family calendar, reminder list and photo stream that you can't unsubscribe from.

Any member of the family can track the location of another member via Find my Friends and within iMessage - although each person must first opt to be tracked like this.

How to use an Apple ID account: Calendars

Family Sharing provides many benefits, including a shared calendar that all the family can use to organise their lives

There are also benefits. The head of the household - or Family Organizer, as Apple dubs him/her - can create accounts for kids under 13, as described previously. They can add a payment card that family members request to use. Annoyingly, this card has to be a credit card - a particular frustration to people that don't have one.

Setting up Family Sharing is easy.

iPad/iPhone/iPod Touch: Open the Settings app, then tap the iCloud entry in the list. Then tap Set Up Family Sharing. Follow the instructions and be sure to provide the Apple ID of each family member when requested. In future to add somebody, repeat these steps and tap Add Family Member.

Mac: Open System Preferences, click the iCloud icon, then click the Set Up Family button. Follow the instructions. In future to add somebody, again open iCloud within System Preferences and click the Manage Family button. Then click the plus button at the bottom left beneath the list of family members.

Family Members can hide purchases from others. Typically this is done by tapping and holding purchases within iTunes (or right-clicking on a Mac).