The filemaker site has a product comparison table.
FM11 and FM Advanced are the same for the user. Advanced has some additional features that are useful for the developer.
FM 10 and FM 11 files can be opened by each other (and some earlier versions also) but only the FM11 client will see the additional FM11 features (such as portal filtering).
FM Advanced has the additional developer feature of saving files as stand-alone runtime versions.
Versions 7 - 11 have the same file format and thus versions 7 - 11 can open the same file. The catch is that if you put features in place that were newly released with filemaker 11, they will be disabled when you use filemaker 10 to open the file.