The "Cloud" is a network of servers - that backs up all of your data safely via a connection from your device to the internet.
This means that if you do any action on the Mobble app, it is automatically backed-up to the cloud, keeping your data safe. Note: If you do anything offline, you can sync Mobble to the cloud when you're back in service.
One of the beauties with having a cloud set-up, is that you can drop your phone in trough and your data is backed up safely. It also means you can connect multiple people to the same property. This means that from the office to the farm Mobble is a way to connect the team. Keeping everyone updated and in-check ;)