Most people probably think aliens are somewhat like us; 2 eyes, 2 arms, etc.
I imagine that aliens are as different from us as an octopus, and as different from each other as well. Some might breathe chlorine or methane, some might be living in temperatures hundreds of degrees below zero or at extremely high temperatures, some may live on planets with ten times the gravity of Earth, and some may have evolved in gas clouds instead of planets.
Their moral systems would not be just like ours. Some things they consider just and honorable we would consider horrifying or horrible, and vice versa.
Some may be more intelligent than we are and some may be less. Some alien civilizations might be thousands or millions of years old. Probably many alien races have become extinct thousands or millions or billions of years ago.
I think it's vastly likely that intelligent alien races exist somewhere else in the universe, but I also think that none of them have ever been to Earth. The universe is just too big and the distances between stars is just too large.
