Roleplaying is a journey of trust you take with strangers. You may now and then start out with a group of people you know in real life, but for the most part, the people you roleplay with have no idea who you really are, or why you are sitting here at the computer. You can tell them if you want to, but most people don't ask. Roleplayers tend to keep personal details private, and don't intrude on one another's space.
Besides, other roleplayers don't necessarily care that much about who you "really are" either. They're there to get to know your character, not you as a person, unless your character first makes a very good impression and they decide that they actually want to be friends as real people. Even though you respect each other as people who share the same interest, there's still a distance between you which either (or both) of you may wish to maintain.
And yet, the relationship you have is one of trust. It's not at all at the same level as a best friend of course, but you still have to trust one another in a very creative sense -- you rely on each other to create interesting things for your characters to share with one another. You're not just buying a shirt from a salesperson or holding the door for a passerby -- you're exchanging behavior and language in an unpredictable and totally interconnected way. Any little surprise a stranger brings to an interaction may completely alter the whole game session and stick in your mind as one of your most memorable gaming experiences. Roleplayers have to trust other roleplayers to help make those experiences positive, even without knowing anything at all about one another. Sometimes two characters can even become very close friends, even though the real people behind them do not.