Synapse launcher: what is the difference between the `locate` command and the simple search?

I love Synapse in Xfce and want to know more about improving its use. I use it to restart, logout or shutdown, launch applications, access files and folders. I have been trying to fix a few problems that affected file access on my second drive, as it involved opening files with executable permission and searching on a NTFS partition . I'm not sure the second problem is fixed: all the files I have searched for until now on the second partition are accessed through locate command — that is, typing the filename shows nothing and I have to press ENTER for locate to run and find them. After being found and opened in this way I would expect them to be found directly (without locate) the next time, but that is not the case. Such files are not even shown in the recent files (opening Synapse and pressing DOWN-ARROW; files appear in the recent files list if accessed from the file manager instead of Synapse). On the other hand, at least some **files and folders from $HOME are shown directly in Synapse without the need for locate to find them**. **What triggers the difference between these and the rest?** I guess Zeitgeist is involved in all normal Synapse search (the one that doesn't involve locate) and the fact Synapse is just showing me the $HOME files is because the problem of Synapse not searching NTFS partition (linked above) is not solved yet! I'm not sure I understand how locate plugin is supposed to work? Is Zeitgeist needing it in some cases or not, or are they completely separate processes?