Hi Cheesielee
Q stands for a quarter note, that is one measure is made up from four quarter notes (4 times 1/4 = one whole measure). If you say "1 - 2 - 3 - 4", these numbers match the beats and you get quarter notes.
"Q." is a bit different. In music notation, "." indicates "one and half times" so "Q." means the length of the note is 1 beat plus one half beat.
Notice the first measure has two "Q." and one "Q". Two of (one and a half beat) notes make 3 beats and then you have "Q" which is simply a 1/4 note (one beat) so you get a total of 4 beats, which is one measure.
"E" is an eighth note, 1/8, aka, one-half beat.
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I don't know "L". Maybe it is a rest", meaning you do not play anything. In TAB, it's sometimes easier to put something in instead of mark the note duration carefully.
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I cannot find "double o's" in this TAB. Maybe it is the repeat sign?
Cheers
Chief