^ Coming from another noob, this might not be too helpful, but I'll try.
The experts can fill in the holes that I'm sure will appear.
Senbatsu - For every single, AkimotoP chooses the members who he believes will fit the image/vocals/whatever other criteria he judges on for the song(s). Those members are the 'senbatsu' members of the single. The only exception to this was Iiwake Maybe, where it was the fans who chose the members rather than AkimotoP.
Kenkyuusei - Literally 'research students', they're basically the H!P Eggs of AKB; not part of the main 'teams', but still fully eligible to be chosen as a senbatsu member (I think).
..I have no idea what LOD means/stands for though.