As with many good games, the idea behind Spaceward Ho! is simple (but vaguely megalomaniacal): rule the galaxy. In order to do this, one must build fleets and colonize planets. There are a few obstacles standing in your way - metal, money, and opponents.
Just like in the real world, every planet has finite resources (I hope that's not news to anyone, except maybe the government). These resources have been grouped into one category, metal. The larger the ship, the more metal it needs. If you run out of metal, well, you're in trouble. That's a reasonable premise, eh?
This brings us the second obstacle, money. Building ships takes money. So does mining. So does supporting infant colonies. Colonies that have large populations create money. Colonies with small populations that haven't been terraformed eat money for breakfast.
This, for lack of a better transition, brings us to the third obstacle, opponents. Opponents can be either computer players or real-live-human-beings on a network. Currently, Spaceward Ho! supports up to 10 opponents - computer opponents can be either Novice, Normal, Smart, or Ingenious. This usually holds true for human players as well. Opponents tend to get in your way when you're colonizing. Everyone's an enemy. Try to colonize one of his planets (either by mistake or on purpose) and he'll defend it to the death.
To help overcome these obstacles, Spaceward Ho! allows you to control how you want to play by letting you budget individual percentages of the gross income to research and colonies. You can divide research into five sub-categories: range (how far a ship can travel without refueling), speed (how fast it can travel), shields (how much damage it can sustain before it goes to the big shipyard in the sky - or in this case becomes a dead hulk floating in space), weapons (I'll bet you can guess), and miniaturization (how little metal a ship can be built with). Similarly, you can split each colony's allocation between terraforming, mining, and shipbuilding. After a planet has been completely terraformed, no more money can be spend on terraforming. Likewise, after a planet has been depleted of all natural resources, no more mining takes place. Hence, eventually all planets will allocate all their resources to ship building, and your imperial nature starts to appear.
Ships have six characteristics: range, speed, shields, weapons, miniaturization (seen these before?), and whether or not it's a colony ship. Colony ships take a lot more metal to build - you can miniaturize ships, but not people, alas. Play as you will - build long distance scouts and explore before you colonize, or build huge colony battleships and colonize and destroy at the same time, or mix and match.