Resource Pack

A resource pack is a special file that can change the textures, sounds, and other components of Minecraft. For more information about resource packs visit: http://minecraft.gamepedia.com/Resource_pack

In Hypixel
Many games on Hypixel require a resource pack to be on to work properly. Some prominent examples are Blocking Dead and Warlords. If you do not have Server Resource Packs on, the game will not work properly.

Turning on Resource Packs
In Minecraft, when you add a server to the list of multiplayer servers, you can change the "Server Resource Packs" option from "Prompt" to "Enabled". When this is done, resource packs will automatically download when you enter that gamemode's lobby or game.