How to Install Minecraft Snapshots
Almost every week Mojang (the developers behind Minecraft) release a new snapshot of the game onto their website. These snapshots are basically previews of the new features that are going to be included in the future versions of Minecraft.
Anyone can download these snapshots but it can be a bit confusing installing them since you are just given the .jar files. To install a snapshot you are going to need to already have a copy of Minecraft on your computer as well as the launcher for it.