I'm not 100% sure what the difference between a yard and a garden is in English, but a ĝardeno usually has flowers, grass and trees, and very often also vegetables. It's used either for recreation or to grow some plants. It can be attached to a house, or also public, like a park.
There is also korto, which is similar, but usually with less grass, less trees, and no vegetables, but surrounded by houses or a wall.
i think a garden is more of a special place to grow vegetables usually in straight rows , or a garden could be a large place with nice landscaping where one would grow flowers. and i think a yard is just more of the property around ones house that one owns. yard can be a pretty vague word.