[mapmap]

It's possible to play local multiplayer without a server. One player can host the game and "open to lan." You will each need your own Minecraft license.

[bombcar]

And beware that mods are basically never tested with "open to LAN" - they'll work until they don't for obscure and unknown reasons.

But if you're using complex mods that break on that; you'll know enough to setup a server.

[lnsru]

Beware, that automatic LAN discovery doesn’t always work for me. Address and port must be entered manually.