I looked up the the word 'cool' in dictionary and discovered that it's a slang, meaning:

1. Knowledgeable or aware of the latest trends or developments 'spent all his time trying to be cool'
2. Excellent; first-rate: 'has a cool sports car; had a cool time at the party'
3. Acceptable; satisfactory: 'It's cool if you don't want to talk about it.'

Well, I have seen people using this word all over the place but my question is, in what sense it is actually used?

It must be a mild slang that most people do not find wrong using. Besides I haven't seen any elderly people using it yet.

Does the use of this word vary with region?

I looked up the the word 'cool' in dictionary and discovered that it's a slang, meaning:

1. Knowledgeable or aware of the latest trends or developments 'spent all his time trying to be cool'
2. Excellent; first-rate: 'has a cool sports car; had a cool time at the party'
3. Acceptable; satisfactory: 'It's cool if you don't want to talk about it.'

Well, I have seen people using this word all over the place but my question is, in what sense it is actually used?

It must be a mild slang that most people do not find wrong using. Besides I haven't seen any elderly people using it yet.

Does the use of this word vary with region?

Edit: It would like to know about its usage particularly in British English.