A session is a scheduled time period during which an Olympic or Paralympic competition takes place. A session contains one or multiple events and is what spectators purchase tickets to in order to attend official Olympic and Paralympic sporting events.
For example, a Diving session could consist of the Women's 10m Platform Semifinal, a Football session could consist of a Men's Quarterfinal match, and a Tennis session could consist of Men's Singles, Women's Singles, Men's Doubles, and/or Women's Doubles matches all within the same ticketed session.