A parenthetical is easy. If it could go into parenthesis, a.k.a if it makes not difference to the meaning behind the sentence, but you still want it there, then it is a parenthetical phrase.
1. Bobby went out to the bar, which he did a lot, and had so many beers he couldn’t drive home.
2. Adrian loves the smell of incense, especially the type in worship, but could never light any when she lived with her mother.
3.She cracked the door and saw they slept, and a little braver than before, pushed the door all the way open.
The “which he did a lot” and “especially the type in worship” are unnecessary to the meaning of the sentence but add extra information. These are the parenthetical phrases. The parenthetical phrases need commas before and after. This gets a bit tricky in concerns to parenthetical phrases and conjunctions.
1. Rusty the wonder kitten loves to play with laser pointers.
1. Rusty, the wonder kitten, loves to play with laser pointers.
2. Rusty likes lasers the light is distracting, and, she chases them around the room.
2. Rusty likes lasers, the light is distracting, and she chases them around the room.
3. Rusty, and, her older brother, Seeley, play every morning at six a.m.
3. Rusty, and her older brother, Seeley, play every morning at six a.m.
Watch conjunctions when resolving parenthetical phrases. They complicate matters. Have fun, folks!!!