"To reserve a seat" means to set aside or save a specific place for yourself or someone else to sit, ensuring that it will be available for you when needed. Full definition
In fact, you are encouraged to purchase / reserve seats for users, as only a certain numbers of users will be allowed to log in to each course per month. (numbershaveproblemstoo.com)
You may reserve a seat in advance so that you'll know exactly with whom you'll be sitting. (museandthemarketplace.com)
When it comes to your entertainment needs, members can access premium reserved seats at various events. (thedigeratilife.com)