I don't have a book, but it's generally like this: providers offer you an email account. Usually, the provider also offers a website where you can access that email account ("webmail"). Some providers also offer mobile apps for access. Email accounts follow some standards, and almost all of them can be accessed via standard email clients (e.g. Thunderbird).

Most have a limited size for your account (e.g. 1GB) which has to fit all your attachments etc. If it's full, you can't receive more emails. Some have automated spam filters etc. Many are free, but their webmail usually contains ads.