What is the difference between Transactions & Registrations

Transactions will only show the billing details relating to the actual transaction that was processed. It will show the billing name, address, state, zip and payment method. It does not include any of the registration details such as preferences, t-shirts and how the amount was calculated. Registrations will show ALL of the form fields and information collected that the user submitted. 

Why does this matter? Often times organizations need to reconcile reports of financial details and this is best done using the Transaction information -- not the registration information. Also, when someone signs up to donate or pay on a recurring basis (like once a month), they submit their request once, but will have additional transactions that process automatically.