Here is a list of the most common terms that occur on sheet music:

allegro – lively, rather quick.
andante – rather slow, a walking pace.
apoyando – rest stroke.( classical guitar )
arpeggio – to play notes of a chord consecutively.
a tempo – in time.
da capo – return to the beginning.
da capo al fine – return to the beginning and play to the word “fine”.
dal segno – repeat from the sign.
eight note – one half of a beat in 4/4 time.
fermata – a pause.
fine – the end.
forte – loud.
fortissimo – very loud.
glissando – in a gliding manner, slurred, to slide.
grazioso – gracefully.
hammer – to produce a new note by forcefully striking the string with the left hand.
harmonic – a chime like tone.
half note – receives 2 beats in 4/4 time.
largo – slow and broad.
legato – smoothly.
lento – slow.
moderato – a medium pace.
piano – soft.
prestissimo – as fast as possible.
presto – quickly.
pull-off – to produce a new note by forcefully removing a finger from the string.
quarter note – receives one beat in 4/4 time.
ritardando – gradually slow down.
rubato – without timing.
segue – merge into following passage.
simile – the same.
tacet – be silent.
tenuto – sustained.
tirando – free stroke ( classic guitar )
tremolo – rapid repetition of a note.
vibrato – to vary the pitch of a note with rapid movement of the left hand.
whole note – four beats in 4/4 time