Your email address consists of two parts – an identifying name and a mailbox. The mailbox is usually identified by the presence of the @ symbol.
Since you get to pick your own email address, you will decide which mailbox to use. There are a variety of options currently available, including Yahoo and Gmail, which happen to be two of the most popular.
When you sign up for an email address, you will be asked to submit a username. You get to choose this username, but since it must be unique, it can take a few tries before you get one that works.
If you chose the username John0101 and signed up for an email account with yahoo, for example, your email address will be [email protected]
Unfortunately, because you are the one who picked the email address, only you will know what your email address is. That;s why, if you want people to contact you on your email address, you'll need to share it with people - the same as, if you want people to visit you at home, you'd need to share your house address.