1. My mother—what a pianist—taught me all I know about music. 2. Yes, I feel that water color is an exciting hobby for an artist.
3. As if he had never seen one before, Jerry stared at the beautiful pyramid.
4. Cambodia, an interesting country, is located in southeast Asia.
5. The Eustachian tube is, of course, essential for correct hearing.

an introductory interjection
an appositive
a sudden break in thought
a parenthetical expression
an introductory adverbial clause