Concepts
Accounts are a list of transaction records by account - think of them like entries in your checkbook and savings account records.
Account records can be detailed, summarized, reported on and filtered. Every account is associated with one account type, and there can be an unlimited number of accounts.
When to use
In this case you can use accounts to track donations of money or in-kind items (caps knitted, books given), things like patients visited or meals delivered, or transactional information like gift shop credits and vacation days.