The Town Hall is a building in the computer game Warcraft II from Blizzard Entertainment. It is the most important building in the game, because it's where you can produce peasants (builder/resource gatherers). These then bring the harvested resources, gold and lumber, to the Town Hall for processing.
So the Town Hall usually is the first building you construct in a Warcraft II game. It can be upgraded to a Keep, which in turn can be upgraded to a Castle. Upgrading increases the hit points of the structure and causes a bonus to gold mining.

The orcish equivalent is the Great Hall.

"Town Hall" is also a general term for any structure of that kind in a Blizzard game. These are the

in Warcraft II, and the in Starcraft. This generalized term allows for statements like "Make sure your Town Hall is protected from all sides". That's an important piece of advice for both Warcraft II and Starcraft, by the way.

A similar generalization is "Peon" for builder/resource gatherer units.