Supplementation

We use the term supplementation for a construction containing an anchor and a supplement, an element related semantically to the anchor, but not integrated into the syntactic structure as a dependent. Supplements are detached prosodically from the anchor, typically having the character of an interpolation or an appendage (an element added loosely at the beginning or end of a clause). Examples are in italic:

• Her father - he's the guy talking to the Mayor - has agreed to finance the deal.
• I finally volunteered to go first, a decision I quickly came to regret.

The definition is from Cambridge Grammar of English Language.