A Transaction contains two halves, the Payment and the Allocation.
Payment
Describes how much was paid, by what method, why it was given and consists of:
Campaign: is the "why" it was given. It is a required criteria.
Payment Method: is the "how" (also affects Gift Aid eligibility). It is also a required criteria.
Allocation(s)
Describes what that money were paying for, how it is being allocated, and consists of:
Product: is the "what" the money was given for, eg donation, membership, merchandise etc (also affects Gift Aid eligibility). It is a required criteria.
Fund: is the "where" - ie. in which pot / project / restricted or general fund does this money sit. It is a required criteria.
Department: which department or cost-centre within your organisation is responsible for this transaction. Optional criteria.
It is possible to have multiple allocations against one payment such as a split gift.
Recurring Payment Instructions follow the same structure.