Following are the main categories of time in a sprint from planning perspective:
1. Vacation / holidays
2. Time for scrum mandatory formalities
3. Time for so called the over head activities
4. Time for unplanned
5. Net planable time
Vacation / holidays : The time when team members aren't available for work due to vacation / leaves / holidays. Some teams do maintain a calendar of leave plans and place it near standup corner.
Time for scrum mandatory formalities : The time for planning, retrospective, sprint demo and preparation time, daily stand up.