Re: How many works about Star Trek in the past??
You should watch everything in the right order:
Deep Space Nine
You can skip Animated Series. It occurs after Original Series, but before Next Gen. Its not essential though.
After Next Gen is Voyager, but that's not as essential either in my opinion. After that is Enterprise. Which actually takes place before Original Series, but was the last series to come out. Sort of like a "prequel" series. Its pretty good.
Personally, I think Deep Space Nine is by far the best. But you should watch Original Series and Next Gen first.
You can watch the movies from the beginning after Original Series... until you get to #7 Generations. At which point you should have watched the Next Generation series first.
I hope that clarifies.
Original Series, first 6 movies, Next Gen, last 4 movies, DS9, Voyager, Enterprise, Animated Series
That would be the order I'd suggest. But you could skip Voyager and Animated.