From these pages you can find generic information about the ISO 20022 messages sent between customer and bank when executing payments.
These messages are defined by ISO 20022 Universal financial industry message scheme (UNIFI). Messages are based on XML (Extensible Mark-up Language). You can get full definition of these messages from the ISO 20022 web site: http://www.iso20022.org/.
SEPA is Single Euro Payments Area and it aims to create a zone for the euro in which all electronic payments are considered domestic. And where the differences between national and intra-European cross border payments stop to exist. SEPA project aims to improve the efficiency of cross border payments and turn the fragmented national markets for euro payments into a single domestic one: SEPA will enable customers to make cashless euro payments to anyone located anywhere in the area using only a single bank account and a single set of payment instruments.