I will try to summarize a post that could otherwise very long, because your questions are so open and speculations can go as far as we want...
No proof. There are people here and elsewhere to talk of many different races, like they know those as biologists on earth know the different species
on earth. This is only speculation.
Credible accouts tend to point towards mainly three races: the greys, the reptilians (sometimes insectoids), the pleiadians/nordics. These seem to
dominate account of 3rd type encounters.
Again, no proof. Only some speculations due to the fact that we can observe some stars very similar to the sun, at distances that seem "more
realistic" than others.
Some people argue that some aliens come from Orion (it is not even a star!), Pleiades (not a star, but a *very* young cluster), Earth (!!!).
Amongst the credible hypothesis of sun sister stars that could possibly harbor life as we know it:
Zeta 2 Reticuli (a planet was announced, later retracted)
18 Scorpii (so far the star that's the most like the sun)
Alpha Centauri (both stars are pretty much like the sun, we haven't found planets there yet though)
There are more, and it is a passionating subject.
The universe has been estimated to be 13.8 billions of years old. We have apparently determined or detected (I've read that somewhere, sorry no link)
that planet formation has occured just about that early too. This thus leaves a possibility for planets that are several billions of years older than
the earth, and even than the sun!
So all hypothesis here are as credible as others: they could be 10,000 years ahead, 1 million, 100 million (this is a little time, cosmologically
speaking), or even maybe several billions of years ahead!
We actually have no proof of:
- extraterrestrial life (this is becoming debatable with the recent Mars explorations, and other possibilities even within the solar system)
- ET's visits, abductions
- extraterrestrial planets/bodies with life
We do have proof that:
- earth-like planets around sun-like stars exist
- life, here on earth, can take multiple forms and exist in extremely harsh environments
- some things that we observe on earth are indeed unidentifiable (although that doesn't mean straight that those are extraterrestrial machines)
However, we have a lot of evidence:
- that UFO's do things we can't do
- that some things land on earth & fly around it, and do intelligent things
- given the amount of witnesses, we have evidence that some ET's have been visiting us, sometimes even interacting.
I hope this gives you a slightly better view. The subject is amazingly vast, and again, your questions are very open. However, it is nice to see that
some people are keen to see the subject with open eyes but with some reason too (as opposed to that lunatic fringe who pretend many many things
without a proof, as a truth!)...
We maybe have no proof, but in real life there are sometimes no need for proofs. In court, many cases are solved or dismissed without proper proof,
but only with evidence. In this case, if I had to be the judge, the evidence I'm being shown points towards intelligent ETs, that do visit us and
Your call to investigate with your eyes and your mind!