Snapshots taken of EBS Volumes are stored in S3. These snapshots get all the durability and availability benefits of S3. You can also copy snapshots to other regions, which is a nice insurance policy against a regional level outage.
If your EBS volume fails, you can then recover from your last snapshot. The more recent your snapshot, the more up-to-date your recovery story is. With the incremental nature of EBS snapshots performing them on a frequent basis is very practical.
EBS also provides "recovery volumes", which you can see from this AWS forum thread.
To my knowledge, the act of taking a snapshot doesn't directly impact the AFR of an active, running EBS volume. Rather, it just makes it easier for you to recover in the event of a failure.