Highways are given numbers. When we refer to a highway, we refer to it by its number. In most of the English speaking world, we would refer to it like "Highway 90" as people have said. When we use this, we would say something like "Take highway 5 from Los Angeles all the way to Sacramento." That just means get on Highway 5 and stay on that highway until you get to Sacramento. "Take" just means "Use" in the context of roads when giving or following directions. The people in Southern California in the US have a different way of referring to a highway. This seems to be local to California, but in Southern California, people would just say "the 90" instead of saying "highway 90." If that sounds strange to other English speakers, it still sounds strange to me, too, but that is very common in that area. So my previous example in Southern California would be "Take the 5 from Los Angeles all the way to Sacramento."

simple highway number 90( it means road or route) like:Colorado State Highway 90 Wyoming Highway 90 so: shall we take highway 90?

That's just the number of a certain highway. Turns out it is the highway running from Florida to Texas in the USA.