This section primarily deals with backing up your site files and keeping them up to date.
You may think or say to yourself, but my web host backups my files for me. In actuality they may, they may not, or they might not run their backups as often as you think. It's also important to consider what would happen in the event you can not access your web hosting account and retrieve your backups, or if your site has been attacked (hacked) that your backups may have possibly also been compromised. It's for these reasons that it's never a good idea to solely rely on your web host for your backups.
Maintaining and working with your backup:
It's always recommended that you have a complete "up-to-date" backup of all the site files on your server also installed in a folder on your computer or on a USB drive that you use to edit files and upload them to your server via FTP. Editing and uploadibg files from your backup will ensure that you always have an "up-to-date" backup in the event something should go wrong with your server and/or site, such as a crash or hack.
It's not recommended that you use your server's File Manager to edit files, doing this can potentially create white spaces and break your site's layout. It's also a bad idea as it doesn't ensure you have a proper up-to-date backup of all your files. Edit the files from the backup of your site with a proper editor such as Notepad2 http://www.flos-freeware.ch/notepad2.html then upload them to your server via FTP. Do not use regular notepad or wordpad to edit files, especially PHP files.
Notepad2 isn't as robust as many pro editors but Notepad2 is freeware and has little or no learning curve because it's like using regular notepad except that it formats html, css and php code properly, and it's really all the average webmaster needs just to do basic editing.
If you need a basic FTP client to upload files to your server, try WinSCP which is a free open source FTP client for Windows. It's available in both a regular install package or a portable version which requires no installation and can even be installed and run from a portable drive (such as a USB drive). https://winscp.net/eng/docs/free_ftp_client_for_windows
Other items you should also backup:
It's also important to do regular backups of your "database" and the "media" folder which contains the photos and images uploaded by your members. Depending on your site's activity this should be done on a daily, weekly or monthly basis. Even if you only did it on a monthly basis, it's still better to only lose some recent content and members than everything.
You should backup the "database" and the "media" folder at the same time so that the links to photos in the database are in sync with the most recent added photos.
You don't need to backup the "cache2" folder, this folder can become rather large over time. In-fact you may want to consider occasionally cleaning out the "cache2" folder. How often you should do this is entirely up to you and can depend on how big and active your site is. There a some fairly busy sites with over 10,000 members that have been operating for years who have rarely ever cleaned out the "cache2" folder and their site's run just fine.
To clean it out delete everything in the "cache2" folder (except for the blank index.html file) and then regenerate your skins in the admin.