What is a BW datasource?

What is a BW datasource? What is meant by maintaining a datasource?

A BW datasource is a structure which is created in the source system and replicated to the BW system. Maintaining a datasource in a source system is doing any changes related to the datasource. It could be adding/deleting fields or checking the flags in the datasource like the hide and selection flag. Also, if the datasource is provided in the LO Cockpit, changes can be made there too depending on how the extraction of data is made for that datasource.