You might want go back to the textbook for more details. Of course, corresponding page numbers are provided. Discourse is spoken or written language used in particular social situations. Given information is the information that was already introduced into a discourse and therefore presumed to be at the forefront of a hearer's mind. It's also called old information.
New information is the converse.
Comment is the opposite notion to topic, the element of the sentence that says something about the topic. A noun phrase is definite when the speaker assumes that the listener can identify its referent. A noun phrase is referential when it refers to an entity. Both fronting and left-dislocation are used to mark given information by moving a noun phrase to the front. The difference is whether or not a moved noun phrase leaves a pronoun after the movement.