This function is often used by mutual aid groups and solidarity funds. Individuals can make grant requests to your page for any amount and submit this as an expense. This then goes through to the page admins to be approved in the same way as the reimbursement or invoice would.
When you set up your page one of the requirements is an Expenses Policy - this is where you can outline exactly what your group gives money out for, and if you are expecting to have individuals request grants this would be the place to outline the sort of grant requests your group would approve.
The grant request function also has a space to add in documents as an attachment, some mutual aid groups ask people to put in proof of address in this section. Your groups' Expenses Policy should outline exactly how you plan to use and distribute your funds.