The latest update in Minecraft has added a Character Creator, allowing you to customize and change the appearance of your character. You will be able to change things like the size and length of the arms and legs, your facial hair, or complete change different body parts. You won't really see much of this yourself since most players play from a POV perspective, but it can be really cool to make a unique appearance if you play with your friends.
So, how do you actually use the Character Creator in Minecraft? You need to access it from the main menu. When you are there, click on "Profile" in the bottom right corner. This will show you all your profiles, and select the one you want by clicking "Edit Character". This will take you to the Character Creator screen where you can see all the different options for changing your character on the right side of the screen.
You will have access to most of the different customizations by owning the base game, but some of the more special ones require a purchase.
Unfortunately none of the customizations are unlocked from doing things in the game, so you have to pay up if you want access to the special ones.