The Tiny Chao garden is found in Sonic Advance (for the Gameboy Advance). It is a "Tiny" Garden that contains one Chao, and one Egg. You can feed and raise your Chao wherever you like!
The first time you open the Tiny Chao Garden, all you will bee is a normal egg.
To hatch it, move the cursor over it and press the "A" button to rub it.
Keep rubbing it and it will hatch!
Now your Chao will be roaming around freely! On the right are its stats.
Underneath the stats is how many rings you have, collected from the main game,
or by playing the minigames.
Above the stats are some information about your Chao.
It will tell you what stage of life your Chao is at (in these pictures it is a Child),
and above that is its name. The game gives the Chao a random name at first,
but you can change this by clicking it with the "A" button.
You can then enter in a new name.
Mood is how it is feeling. The more full up it is, the happier it is! Pet your Chao once in a while by pressing the "A" button on it and this will make it feel more loved. Sometimes weeds may grow in the garden. Make sure you pick these out because if you leave them it will make your Chao feel like it is not wanted!
This is from the first Sonic Advance game.