Can you summarize the categories briefly under current counter trade?

Can you summarize the categories briefly under current counter trade?

Current counter trade can be categorized as follows 1) barter: the direct exchange of goods and services which is completed in a short period of timet； 2)counter purchase: the assumption by an exporter of transferable obligation through separate but linked contract to accept as full or partial payment goods and services from the importer or importing country; 3) buyback: an agreement by an exporter or plant and equipment to take back in the future part of the output produced by these goods as full or partial