File compression allows you to save online time and storage space by compressing your data into a zip file.
This could be one archive for all backed up files or many archives for many files. You can also set up the compression quality, which also affects the amount of space the backup file will occupy on the server. The higher is quality, the less space the archive occupies in the account, but the more time it requires for compression.
Read about online backup service and find the advantages of it.