Wolfram|Alpha and Wolfram Language are two completely different things:

Wolfram|Alpha is a natural language computational engine which takes queries and computes custom answers based on back-end knowledge databases and a large amount of Wolfram Language algorithms.

Wolfram Language is a computational (programming) language. There is a good 'fast introduction' for it here:

http://www.wolfram.com/language/fast-introduction-for-progra...

The full reference documentation for the Wolfram Language is located here:

https://reference.wolfram.com/language/

(It's extremely well-documented with extensive examples for every function).