Heroes of Might & Magic III is a turn-based strategy game, and a good one. The single-player game’s six campaigns take you through the war to claim the kingdom of Erathia from the perspectives of the various factions- in simple terms, the good guys, the bad guys and the mercenaries. 
 

The basic principle behind the game is simple- manage your resources, build armies, defeat your enemies. Familiar enough, what? Gameplay is turn-based, and each campaign consists of several levels. Each level is one large map, scattered about which are towns, buildings, resources and land features, not to mention monsters hanging around guarding resources or particular paths. You have to guide your heroes about the map, to find resources, treasure and magical artifacts, and build up your towns

 Each turn, you collect a certain number of resources -wood, gold, gems- depending on how many mines you control. Using these resources, you can upgrade your towns to produce more resources or else to build more powerful units. 

As your heroes gather experience through combat and exploration and gain various skills & spells, you can put them in command of your armies. Where did these armies come from, you ask? You have to train them at your towns and castles, and these troops must fight under the command of a hero- they cannot be sent out on their lonely own, though they can be garrisoned at any of your castles or towns. This time around, you have eight classes of heroes to choose from, each with its own town type and troops. The eight town types are Castle, Dungeon, Fortress, Inferno, Necropolis, Rampart, Stronghold and Tower. These town types are quite distinctive, each town type having some unique structures, such as the skeleton transformer for the Necropolis or the lighthouse for the Castle. Each town also has seven unique creature types. These towns can be upgraded, either to defend the town itself, to upgrade your hero when he’s in town or to upgrade your troops. By building additions to your town, you can also train different types of troops. There are temporal limitations, though. Each turn is a day, and you can only make one upgrade per turn to each town, and you only get new troops at the beginning of each week.

All right, all that is the backdrop. Let’s talk a little more about the heroes. Your heroes, as newcomers to the series would have guessed from the title, are central to the game. All of them are listed in the game manual, along with their stats, and all heroes have four primary skills- attack, defense, knowledge and power. These will determine how well (or otherwise) your hero will do in combat.
Heroes can also have up to eight secondary skills, which have various effects ranging from increased proficiency in certain types of spell to increased movement. Various artifacts are also scattered around the maps, and a hero who finds these gets bonuses. Generally, you will have to fight to get to the artifacts, though.