Most tools have many different variants and skins.
Skins will function the same as the tool they are a skin of and are usually more expensive. Some tools add new nerfs or buffs (like Bloomerang, which is similar to the Boomerang, but it only hits once and you get a vertical boost when you collide with it and has a higher cooldown)
Tools can also give players Status Effects that can modify the gameplay of the players.
Variants will change the look and may add some buffs and nerfs to the tool. Some variants will also have special effects (e.g. the snowball can cause chill for up to 6 seconds but has no knockback or stagger).Some tools are only available at certain times in a year the ones that do have a small icon on the corner. There are currently no Spring or Summer exclusive skins. Go here: If you want to create your own tier set for tools.