Double click on a track name.  For the attached picture, the track name is GTR. Pro Tools will bring up the track name dialog box. Then, if you want to name more tracks use cmd-up/down arrows (or left right arrows) to cycle to other tracks.  I will often use copy and paste if the track names are similar.  TAB will cycle between track name and comments.  I like to add comments like microphone type/polar pattern/pad or special preamp settings.  Maybe add discriptive placement notes like 2" mid-speaker cone close mic or room ambient microphone in the comments section.