Encryption is hard to understand, but this three minute video does a great job explaining how public key encryption (aka public/private key encryption) works, and how it can be used to send messages between people, websites or computers) securely without having to send the key (password) with the message.
Encrytion viruses such as Cryptolocker, Cryptowall and Teslacrypt silently encrypt your files (photos, documents, everything) so you can’t open them without paying around £400 to the bad guys for the decryption password. Antivirus might not protect you. The new viruses also encrypt online storage and backup, so having an online backup or online storage might not help you. What you need is a memory stick or an external hard disk that you can connect whenever you want to do a backup and disconnect when the back is done.
Please, if you value those photos and files, make sure you have a proper backup that you control (ie more than one copy, not online). If you want me to help you set it up, including recommending any memory stick or hard disk you need, then please get in touch.