Transaction Log and mirroring - looking for dumbest explanation possible
The transaction log is a important method to restore your database in a specific time. If you have a large database > 500 GB and if you must restore your database from a full backup, this will cost very much time. Also if you full backup your database everytime, think about how long this backup could take.

A very easy concept for SQL Server can be:
Set Recover Model of your Database Full

Create a Maintenance Plan(1) in SQL Server:


Do FullBackup every Week maybe in D:\yourbackup\FullDBBackup.bak
Do Differential Backup every two days in D:\yourbackup\DiffBackup.bak
Do every 2 houers Backup your Transaction log in D:\Yourbackup\Tranlogbackup.trn


Create a Maintenance Plan(2) in SQL Server:


Delete all older Files 8 days from D:\yourBackup*.bak
Delete all older Files 3 Days from D:\yourBackup*.trn


In this case, you are able to recover your Database in a specifc time, very fast very easy. 
SQL Server will automaticly manage your "Backup" files, older files will be deleted after your specific time range.

I would suggest that you read about SQL Server Transaction Log here:

http://www.sqlservercentral.com/articles/Design+and+Theory/63350/

For using the Maintenance Plans in SQL Server just ask BING / google :D

you should build a small test db and test this before you go in production