The first runs in Mac OS X's Classic environment, while the second is Carbonized for Mac OS X. Both updates work in previous versions of Mac OS.
The Sims Carbon updates the original (1.x) version of The Sims for Macintosh. It requires an existing installation of The Sims 1.x. The Sims Carbon can't be used to update other The Sims games such as Livin' Large or The Sims House Party.
Both updates, which are free to download, fix problems in the original Sims - including problems with skin textures and low-level mouse button handling. Cursor screen pinning has also been fixed.