Full backup is a full copy of your entire data set. They are time-consuming and often require a lot of disk space.
Differential backups only backup up the data that has changed since the last full backup. If you have a full backup on Sunday and differential backup every week day nights, you only need the full backup and the last differential backup in order to restore the database.
It is a little different from Incremental backups in that incremental backup only back up the data that has changed since the previous backup. If again you have a full backup on Sunday and incremental backup every week day nights, you will need the full backup and every incremental backup since the full backup in order to restore the database. It is more time consuming but each incremental backup takes up less space than a differential backup.
Transactional backups allows you to restore data since the last transaction. The database needs to be set to “Full” recovery model in order to use transactional log backups. Transactional log will continue to accumulated until a transactional log backup has been made. Running a full or differential backup will also clear up the transaction logs. If left unmanaged, the transaction log can end up taking up a lot of space so be carefully went using transactional backups.