On Mac, can one easily automatize repetitive work? Let's say I have some repetitive work on Mac which requires click menu A, then give some input, click button on and on.

Can anyone easily automatize these kind of tasks with Mac? What kinds of options do I have for it?
Automator on Mac is certainly one of the most underused apps. Using it doesn't require a long time of learning. All you have to do is to understand the way it works.
You'll find the answers to your questions in this tutorial.

By the way, in case you'd like to get the most out of your Mac, check this out also:
http://automator.us/leopard/index.html

Let me know if you managed to create your first Automator workflow ;)