The normal progression of a sentence is interrupted by extra information or explanations enclosed in commas, brackets or dashes. The extra information can be a single word, a phrase or even a sentence.
- We (myself, wife Jessie and daughters Wanda and Jennifer) boarded our boat 'Queen', a Duchess class vessel barely a year old, at Black Prince Holidays' Chirk boatyard.
- The boats have remarkably few controls and we were given a thorough briefing about 'driving' ours–along with advice on mooring, lock operation and safety considerations–by Kate, who even set off with us for a few minutes to ensure we were confident.
Depending on the importance attached to it, additional information can be enclosed in brackets, commas or dashes.
Brackets - not important
Peter (Carla's boyfriend) bought the tickets.
Commas - neutral
Peter, Carla's boyfriend, bought the tickets.
Dashes - emphasized
Peter–Carla's boyfriend–bought the tickets.