KeePass is my favourite for password manager. In Linux, there are KeePassX and KeePass 2. There are several differences.

KeePass has two versions, they are KeePass version 1 and Keepass version 2, namely KeePass 2. They are using different file formats: kdb and kdbx. KeePass is natively runnable in Windows; KeePass 2 requires .NET Framework 2.0 (and above) or Mono (and above). That is why, KeePass 2 is able to run in Linux. Then, KeePassX is a port of KeePass, so that it works as cross-platform, including Windows. However, KeePassX is not based on KeePass 2. Thus, it cannot read/write kdbx. But, there is KeePassX version 2 in the alpha stage, which is available in GitHub.