“Activities” are time blocks that can be reserved, either through classes with an instructor (i.e. Aqua fit or Spin class) or access to spaces (i.e. gymnasium amenities, lane swimming, skating, etc.). These activities would have been considered drop-in activities before Covid-19.
"Programs" are pre-registered, scheduled instructor-led classes, such as swimming lessons, spins class, art class, etc. Most programs have a number of classes spanning over days or weeks.