A gliss. (short for glissando) is a note that you play and then slide your finger (somewhat) quickly along the string so that each note can be heard in between.
The "hold chord" at the end of line 2 just means that you are going to fret the entire chord and pick through the notes without letting go, letting it ring.
Here's a good place to start for general musical terms:
Glossary of musical terminology - Wikipedia, the free encyclopedia
After a while you just get used to them.
Peace,
Kevin