A heavy fighter is someone who is authorised in the SCA as a combatant in (suprise surprise) heavy fighting. Wielding swords, shields, maces, axes.. these people just beat the crap out of each other with sticks of adapted rattan (or at least attempt to). There is also a special breed of heavy known as the stickjock or stickchick.
Resources for heavies
A good resource for heavy fighters that are just starting out is Duke Bellatrix's fighting manual which can be found at:
It is free to use, and downloadable in both pdf and MS word versions.