There are two major types of data load available based on the load process.
1.Full Load (Bulk Load)
The data loading process when we do it at very first time. It can be referred as Bulk load or Fresh load.
The job extracts entire volume of data from a source table or file and loading into truncated target table after applying transformations logics.
In most of the case, it could be a one time job run after then changes alone will be captured as part of an incremental load. But again based on business need, it will be scheduled to run.
2. Incremental load (Refresh load)
The modified data alone will be updated in target followed by full load. The changes will be captured by comparing created or modified date against last run date of the job.
The modified data alone extracted from the source, the job will look for changes in the source table against job run table, if change exists then data will be extracted and that data alone will be updated in the target without impacting the existing data.
If no changes are available then the ETL job will send a notification with no change available between source and stage/target message.