DAC supports different kind of data extraction and loading combinations to give more flexibility over the kind of data transformation that happens.
Full Extract and Full Load: Loading of data warehouse first time happens in this way
Full Extract and Incremental Load: This comes in a situation like when you have to pull data from a new source and load it into the existing table in warehouse. It will have an additional logic whether to insert/update the record in cases of handling data integrity.
Incremental Extract and Incremental Load: This would be the regular process where the data loading happens every night which captures only the new or changed records.