A minigame server hosts short, self-contained games such as Bedwars or Skywars. Players wait in a lobby, are placed in a match, play it out and return. A minigame setup packages the lobby, the queue that fills matches, the arenas and their reset, the game rules, and often parties and statistics.
The design question is scale. Each match is a separate world or arena, so a busy network runs dozens at once, and how a setup creates, loads and clears them decides how many players a machine can carry. Some setups run everything on one server, while others spread games over several servers behind a proxy.
What to look for in a minigame setup
Games included: check which games ship with it and whether you can add maps or new modes.
Arena handling: find out how worlds are copied and cleared, and what the recommended player counts are.
Proxy and multi-server support: see whether it runs on one server or needs a proxy network, which changes your hosting.
Server software and version: confirm the platform and the Minecraft versions supported.
Maps and licences: maps are creative work, so check what rights come with them.