How much of space have we discovered?

The amount of space that planet Earth at present have seen and know about is merely a tiny speck in the whole universe. I myself personally, believe that there are identical solar systems to ours further out there and that there are human beings just like us but they live so far away that it would be impossible to ever find out or communicate with them. Maybe one day in the far future they will find out but i will be long gone by then. So the answer for your question is that we have only discovered a tiny part of the universe as we don't have the resources to see any further into space.