The cloud is basically an online storage facility, to which your data is usually backed up automatically. There are a huge selection of cloud storage providers. Some of these are free (but limit the amount of storage available to you) and are probably best for storing treasured digital photos etc.
Others have a small weekly, monthly or annual charge but allow much greater scope for your backup storage.
The great advantage of cloud storage is that all your connected devices are backed up automatically.
Try these providers.