Terminology in music plays a very big part because it tells you how to play the music. Music isn't just notes, it has feeling and expression. Terminology helps you determine how the piece should be played.
These are the basic terms that you should be familiar with when first starting out. There are hundreds and hundreds more, so we suggest that you keep a music dictionary handy in case you come across an unknown term.
Legato-smoothly (indicated by a curved line over or under the
phrase of music)
Stacato-sharply (indicated by a dot above or below the note head)
Crescendo-gradually play louder
Decrescendo-gradually play softer
pp-pianissimo (very soft)
ff-fortissimo (very loud)
D.C. Al Fine-play to the end of the piece, go back to the beginning and play until it says "Fine"