KeePass is an open-source password manager. There are many compatible programs, many with confusingly-similar names, like KeePassX. KeePass2 is the new version of KeePass, which uses a new file format. Most KeePass-compatible programs, including KeePassX, support the old file format and the new one.
Sure, but why prefer say KeePassX over KeePass2?
Unless they know something I don't, I assume people recommending KeePassX are not Windows users.