Java Edition users of Minecraft will need Java installed. World packs, like Aquatic Life, will require making a new World for that add-on. Keep in mind that some add-ons, like texture packs, can be applied directly to your existing Worlds or Realms, but some that change the nature of the game a lot will require you to make a new Realm or World. There are add-ons that come free with a Realms Plus subscription, with all other packs costing real-world money (via Minecraft Coins), which can be bought in the store directly.
Those playing on the Bedrock edition on consoles or through Windows can grab add-ons directly through the marketplace. Using add-ons in Minecraft Bedrock Edition Players on Java Edition will use mods that they can dig around for, mostly at no cost. Players on Bedrock Edition will primarily use add-ons, which can be purchased for real-world money in the marketplace. Minecraft players can customize their games using a plethora of add-ons or mods, depending on which version they’re playing.