Backup

From Backing up a site

Backup the MySQL database using standard MySQL commands.

It is recommended to have a backup of ALL the files in case any have been modified.

If you don’t backup everything:

/sites/all/modules/

Failure to do this may leave you with no clear example of which modules you had, and what versions they were.

Administer, Site Configuration, File System

The folder where (uploaded) files are stored. On my site: sites/default/files

/sites/

Contains themes, logos and embedded images.