Pre-releases are the equivalent of beta releases – the update is mostly ready and only small changes and bug fixes will be made from now on.
1.17.1 had no snapshots, as it will not add new features and instead just focus on fixing issues with the full release of 1.17.
This pre-release fixes a couple dozen issues, most of them reported during development of 1.17, relating to issues like disappearing ender pearls and font issues.
However, this pre-release also includes a couple of minor changes. Cauldrons now fill up with powdered snow twice as often, drowned zombies now drop copper more often, the blue axolotl can no longer spawn naturally, and screaming goats can be bred from regular (non-crazy) goats.
As it is in the pre-release stage of development, 1.17.1 is expected to release relatively soon, within the next few weeks or so.
Java Edition 1.17.1 is not to be confused with 1.17.1 on Bedrock Edition, an update released last week for the Nintendo Switch to fix a server issue.