While in future titles we get to see The Mysterious Planet from orbit, for now we don't know much at all. It's a densely forested planet, with an atmosphere high in (toxic) oxygen, and covered with what appears to be several artifacts from a civilisation that once lived where you now stand.
This is where our plucky explorer first lands, and where we meet the Red Pikmin for the first time. Other than that, there isn't much of note. There's a large supply of pellets to replenish your numbers, and there's two very dangerous enemies you can fight to reclaim two parts of your ship, but that's all.