With memberships, you can define your own duration/term of the membership and allocate a set number of sessions/classes which can be used.
If you have a Payment Integration active, then you can also link memberships to automatic recurring payments.
Here's a quick video on how to set this up:
Adding a new Membership
To add a new membership, click the '+' icon:
Fill in the details for the membership:
Note: you can have any mixture of sessions or classes. For example you could have 10 sessions & 0 classes, or 10 classes & 0 sessions, or 10 sessions & 10 classes.