Full backup results in:
1. Backs up any activity that took place during the backup
2. Backs up any uncommitted transactions in the transaction log. (When the database is recovered from this backup, the uncommitted transactions are rolled back.)
Transaction log backup results in:
1. Backs up the log from the last successful [Backup Log] statement to the end of the current log.
2. Truncates the log up to the beginning of the active portion of the log and discards the information in the inactive portion.
Active portion of the transaction log starts at the point of the oldest open transaction and continues to the end of the log.
A Tail log backup includes the portion of the log that has not been backed up (active portion) - this backup does not truncate the log and is used when the data files are damaged but the log is undamaged.
Differential backup results in:
1. Backs up the parts of the database that have changed since the last full database backup.
2. Backs up only the extents that changed since the last base backup.
3. Backs up the activity that took place during the differential backup and any uncommitted transactions as well - this is similar to full backup.
