Logical and physical backup
One of the methods to create a backup is to stop a database completely and then copy all of the files to a safe location. This is easy to do and doesn't require special tools. However, while making the backup, your database is unavailable. This type of backup is called a physical backup.
Another way to create a backup is to export the data for all the tables and other database objects into a file that can be imported again. This is a logical backup as it doesn't copy the physical files but extracts the logical objects from the database. The benefit of this is that you don't have to shut down your server while taking the backup. The drawback is that the restores generally take a lot longer than a physical backup.
There are two alternatives to taking physical backups. The first one is taking a snapshot. You still need to stop the database server, but the time spent waiting for the copy is generally a lot less, as is the storage space required...
