Mojang Team continue to please the players with new updates that are a prerequisite for the release of Minecraft 1.13. All snapshots contain a huge number of bug fixes and new content. Be aware that this and the following snapshots are aimed at the technical component of the game and you’re unlikely to see any drastic changes.
Either way, Snapshot 17W47A will show you new trapdoors, buttons and pressure plates from different kinds of trees. Perhaps this is the most notable feature that you can see. Also, developers are trying to remove the limit for the number of blocks, which is very difficult to implement.
Therefore, 17W47A and 17W47B are very unstable beta versions, don’t forget to make backup copies of your worlds.