WordPress sites can be backed up effectively so that, if anything goes wrong, you can restore the files and data you need. You will be able to back up the database easily, which helps to protect all of your posts, comments and links. You should probably back up as often as you can so as not to lose anything that might be important to you. Data can be corrupted in a number of ways so you can never be too careful if your WordPress content is important to you.
WordPress recommend that you keep three different backups to be as safe as possible. As well as backing up your database, you can use things like hard drives and web disks. If you want your backups to be smaller, you might want to consider not backing up plugins as these can add a lot of data that is usually unnecessary. You can automate backups if you wish.