Before beginning, the player is able to choose whether to play as a girl or a boy, and name themselves. At the beginning of the game, the player's deceased grandfather visits them as a spirit and asks them to take over his farm. He implores them to succeed him as a Ranch Master, stating he will check on the player at the end of each winter to determine his progress. The player must develop their farm by growing and selling crops, and raising livestock to reach this goal. If the farm meets his criteria for you to be a Ranch Master, the player may receive extra tools; if he thinks the farm doesn't, a Game Over is given.
Crops are the primary source of income in Harvest Moon GB. Different seeds can be sown during different seasons, but any seed sown outside of its designated season will not sprout. After being planted, the seeds must be watered every day until they can be harvested. All harvested crops (along with anything able to be sold) may be put in the shipping bin to be sold. Almost all crops require active farming and maintenance, although every day, the player can harvest two Mushrooms from their underground cellar to sell.
Either a dog or a cat may be chosen as a pet. If you choose a cat, wild dogs won't attack your chickens; if you choose a dog, moles will not destroy your crops. The player also receives a horse early in the game, which when grown can be used for farm work, riding, and shipping items.
There are two types of livestock - cows and chickens. Cows can produce milk, which can be turned into cheese and butter, and chickens produce eggs. Both livestock can reproduce: cows by giving them Miracle Potion (equivalent to artificial insemination), and chickens by hatching their eggs.
There is a wide variety of tools in Harvest Moon GB. At the beginning of the game, the tools available are the axe, hoe, hammer, watering can (obtained after buying your first crop seeds), and sickle. These tools may be improved, turning into "super" tools. The player may also receive a fishing rod, pickaxe and umbrella after reaching their grandfather's goal.
Source: Wikipedia, "Harvest Moon GB", available under the CC-BY-SA License.