Someone paying for a unit is not always the person renting it — a parent paying for a student, a company card covering an employee, a friend helping out. Your storefront checkout can be set to handle that, so the rental ends up in the right person's name.
Where the setting lives
In the Storefront builder, open Components → Checkout. The Tenant name setting sits in the component settings, beside Contact details.
The three options
Use the cardholder name as the tenant name — checkout collects one name and uses it for both. This is the default, and it is what checkout did before this setting existed, so leaving it alone changes nothing.
Require a separate tenant name — checkout always asks for the tenant's name as its own field, whoever is paying. Worth choosing if you regularly rent to people who aren't paying for themselves.
Ask whether the tenant and cardholder are different — checkout shows the renter a tick box reading I'm renting this unit for someone else. Tick it and a Enter the tenant's full name field appears; leave it alone and the cardholder's name is used, as before.
What to expect
The name you collect here is the name on the lease and on the tenant record, so it is worth getting right at the point of sale rather than correcting it afterwards.
The setting applies to that storefront's checkout only. If you run more than one storefront, set it on each.