Farming and eating
Grow crops and make food.
You can grow wheat for Bread. Bread restores 30 health. Consumable healing shares one cooldown, so eat between fights.
Planting a field
Find exposed soil with light and water. Grass spreads onto bare soil, so clear it before sowing your seeds. Wheat, flax and cotton seeds can each be made from their grown plant by hand, at a rate of one plant to two seeds. Most grown plants can be turned back into two seeds this way. The Hand recipes show how.
Wait for the plants to grow, then cut them with a Harvesting Sickle. It cuts the crop without digging up the soil. Mining a crop can destroy it without a useful harvest. Use your wheat to make bread, and save some seeds for the next planting.
If nothing grows, check the soil, light and water. Crops will not grow in a dark cellar. Keep your field away from furnaces, too. These crops are flammable, and most ignite below 100 °C. Cotton ignites at 60 °C, the lowest ignition point in the game.
Grass seed is different
Most seeds, including oak, birch, wheat, flax, cotton and flower, are materials. Place or scatter them on soil with air above it. They fall and germinate where they settle.
Grass Seed works differently. Aim at the empty air directly above soil. It converts that cell instead of falling onto the soil. Aiming at the ground will do nothing.
For another source of crafting materials, see Bees and wax.