Cool (adj) like awesome means ‘great’ or ‘fantastic’. It also shows that you’re okay with an idea. Be careful the normal meaning of cool means a little cold so you have to listen to it in context to understand what’s being said.
Example 1)
“How’s the weather in Canada these days?”
“It’s getting cooler. Winter’s coming!” (This is the literal meaning a little cold)
Example 2)
“What did you think of my new boyfriend?”
“I liked him. He seemed like a cool guy!” (He seemed like a nice guy).
Example 3)
“I’m throwing a party next week for my birthday. Do you want to come?”
“Cool! Sure, I’d love to!”