- Full backup: Backup all targets.
- Differential backup: Backup the changes since last full backup.
- Incremental backup: Backup the changes since last incremental backup.
|INCREMENTAL LEVEL 0
|Cumulative Incremental Backup
|INCREMENTAL LEVEL 1 CUMULATIVE
|Differential Incremental Backup
|INCREMENTAL LEVEL 1
It's obvious that Oracle backup terminology deviates from the current industrial convention. I don't think Oracle will follow the industrial convention to resolve the confusing terminology in the future because of backward compatibility issue out there.
Therefore, you should distinguish industrial terminology from Oracle backup syntax when you were talking to SE or architects, otherwise, they could depreciate your expertise.
Wikipedia also criticizes the meanings defined by Oracle:
It is important to remember the industry standard meaning of these two terms because, while the terms above are in very wide use, some writers have been known to reverse their meaning. One case, for example, is the one found at The Elder Geek website.For more information about Oracle Incremental Backup, please refer to the official 12c documentation:
Oracle Software also leverages a backward description of differential backups in their DB product as of May 14, 2015: 
Quote " Differential Incremental Backups In a differential level 1 backup, RMAN backs up all blocks that have changed since the most recent cumulative or differental incremental backup, whether at level 1 or level 0. RMAN determines which level 1 backup occurred most recently and backs up all blocks modified after that backup. If no level 1 is available, RMAN copies all blocks changed since the level 0 backup. "
RMAN Backup Concepts : Incremental Backups