Many churches have side chapels, like little churches within the main church. Side chapels are used for small services, often for weekday Mass or Exposition
Chapels are the name given to the Union bodies in specific workplaces. Our many atheist members will be relieved to hear that there is no religious connotation to this. Chapels are led by an MoC (Mother of Chapel) or an FoC (Father of Chapel). The distinction should be obvious.