Where is Coinbase available?

Could you please elaborate on the availability of Coinbase? I'm particularly interested in knowing which countries or regions Coinbase operates in. Are there any specific requirements or restrictions for users to access Coinbase services? Additionally, are there any plans for Coinbase to expand its services to new markets in the future? I'm also curious if there are any notable countries or regions where Coinbase is currently not available and if there are any reasons behind that.