The basic meaning of the character "看" is "to look at / to watch". Of course there are extensions. For example "看书" means to look at a book (in other words, to read a book), "照看" means to look after. But you can't say "看" is to read. It's just coincidence that they are the same thing when the object is a book.
What does "过" and "到" mean?
The character "过" itself means "go across" or "pass through". For example, "过河" means to go across a river.
The basic meaning of "到" is "arrive". "我到北京了" means "I've arrived in Beijing."
When you use "过" after do, it means you did something in the past, and it becomes a part of your experience.
When you use "到" after do, it means you succeed at doing something. It tells you the result.
So, "看" is merely the action of looking.
●"看到" means you see/find something. (emphasizing the result of looking)
-他 看到 一列火车。
-He see/find a train.
●"看过" means in the past, you've seen/looked at something. (emphasizing the time)
-他以前 看过 这列火车。
-He have seen this train before.
-他看过了,什么都没看到。
-He have looked, but didn't see anything.
Actually you can also say "看到过", which means you found/saw something before. (both what and when)
-他在这里 看到过 一列火车。
-He saw/found a train here before.