A garden is a piece of land that's used to grow flowers, vegetables, or other plants. Your grandmother might be so proud of her rose garden that she gives every visitor a tour of it.
A vegetable garden is often planted in straight rows, sometimes within a raised bed. Flower gardens can take all sorts of shapes, from tidy to meandering. When you work in your garden, pulling weeds or planting seedlings, you garden. In the UK, a garden is what's called a yard in the US — any bit of land just outside of a house. The phrase "garden variety" means "ordinary:" "Oh he's just a garden variety mixed-breed dog, nothing fancy."