A modpack bundles dozens or hundreds of mods into one install—think automation (Create, Mekanism), magic (Botania, Blood Magic), exploration biomes, quests, or progression gates like SkyFactory. Servers run a fixed pack version so everyone’s client matches; you usually install via CurseForge, Modrinth, FTB, or the launcher the owner recommends.
Listings tagged Modpack point to those communities—read the description for the exact pack name and version, then copy the IP once your client is ready.