In terms of what's available to you for free, the Best practices to backup Salesforce data lists:
If you do some sort of custom work with the API, you could have a high frequency of backups (assuming you don't hit API limits), but the Data Export Service allows you to only generate backup files manually once very 7 days as it's most frequent option (and it could be delayed).
If, you haven't backed it up by taking those actions above, there is still the Salesforce Data Recovery Service (was reintroduced after being announced it was going to be retired), but it is paid and is not a quick turnaround from my prior experience. It's essentially a last resort option where you create a case with Salesforce.
All of the above is only concerned with data backup. I would argue, the recovery or restore process is just as important and the more difficult to tackle. The above may leave you with many excel/csv files, but I would argue it would be near impossible to restore a large data loss from that type of backup. Imagine attempting to insert records across many different objects with x amount of relationships between them - that's the challenge. There's nothing, as far as I'm aware, in free tools to help with this situation.
Hence, why paid service exist to tackle both data backup & restore. There's the Ultimate Guide to Salesforce Backup Solutions which lists various services
Salesforce did recently mention a pilot for a Salesforce backup and restore service built natively on the Platform.
Finally, based on customer feedback, we are pleased to announce that we will pilot Salesforce backup and restore services built natively on the Platform this summer. We’ve co-designed these services with customers and we expect to deliver the performance, speed, and scale that you’ve come to expect from the Salesforce Platform while continuing to provide additional ways to innovate and extend these capabilities through our vibrant ecosystem.
Edit: Backup & Restore was announced at Dreamforce 2021