I should mention about a tool that deserves to be described specifically – rsync.
This tool is well known by system administrators but not as much by home users. But this tool has promising capabilities for them as well. If you’re a backup lover like me (your photos, documents and etc.) and if you’re doing a copy&paste for that, rsync is a life saver.
rsync simply synchronizes your destination directory to be same as your source directory. It does this process with very effective way. It calculates differences and only copies/synchronizes the differences of files and related directories. The destination can be a remote machine (i.e. remote_user@remote_ip:/destination/directory/path). So I backup my home folders contents with my external HDD with:
rsync -avz source-dir destination-dir
Do not use copy&paste (including console cp commands) for backup purposes. Use rsync.