Cosmetics are a way for you to enhance your gameplay with visual things. There are hundreds of cosmetics so make sure to play as much as you can in order to get them all!
The first kind of cosmetics is in-game cosmetics. These are cosmetics that appear while you are playing minigames. There are different categories of in-game cosmetics such as Kill messages, Win effects, Kill effects and Projectile trails. These in-game cosmetics can be found in all minigames, but there are extra cosmetics in Bedwars which are as follows: Bed destroy effects, Fireball trails, Wood planks skins and Shop keeper skins. Note that in-game cosmetics don't affect the gameplay at all. It's only visual addons.
The second kind of cosmetics is lobby cosmetics. These are cosmetics that you can use only in lobbies. There are also different categories of lobby cosmetics such as Morphs, Suits, Particles, Cloaks, Heads, Gadgets, Mounts and Click effects. You can use these lobby cosmetics in all minigames lobbies and in global lobbies too.
Seasonal cosmetics are cosmetics that you are able to obtain only during special events such as Halloween, Christmas, Easter and Summer. During the rest of the year these cosmetics are unavailable. There is a last kind of Seasonal cosmetics which is called Clan. These cosmetics can be obtained with Clan Lootboxes. Instead of other seasonal cosmetics, Clan ones can be unlocked during the whole year, all it needs is Clan Lootboxes which you can get each end of a Clans Season. Find more information about lootboxes and clans in their dedicated section.
In-game cosmetics can be obtained by opening Brain Washers in minigames lobbies. Note that cosmetics obtained from a specific gamemode are available only in the gamemode you unlocked them. It will say that you didn't unlock them if the gamemode is not the same even if this is the same cosmetic.
Lobby cosmetics can be obtained by opening lootboxes. However, these cosmetics are the same in all the minigames lobbies. It means that if you unlocked one of them in a specific gamemode, you will have it in all the minigames lobbies and even in global lobbies.
NOTE: You may also find answers to your questions on our forums.