I would like to learn about games (strategy) algorithms especially about how do enemies algorithms works ?
Is there any good place for beginners?
There are many aspects for AI in strategy games, but keep in mind that there is a big difference between Realistic AI and AI that makes a game fun to play. Cheat where you can while not making it obvious to the player that the enemy is cheating.
AI Game Programming Wisdom books http://www.aiwisdom.com/
Also gamedev.net has a huge collection on AI articles and a good forum with lots of information. (http://www.gamedev.net)
Game Programming Gems feature a section on AI as well, but when AI is what you want, go with the AI Game Programming Wisdom books.
Here is an overview on RTS specific articles: http://www.aiwisdom.com/ai_genrerts.html Also look at Pathfinding, possibly some neural networks / genetic algorithms when you want to play with that, although it might be a bit overkill when you're just starting out.