Mark V can visually display information on entities in a map using tool_inspector. Switching weapons changes the information displayed.
If an entity has, for instance, edict #78 -- type edict 78 in the console to see detailed information.
You can also do viewpos, scr_showpos and setpos. If you type viewpos and then move and type setpos, you will teleport back to the location of viewpos. You may also enter x,y,z coords. scr_showpos will display your x,y,z on-screen.