The adjective virtual is used to describe something that exists in essence but not in actuality. You may have made a virtual friend on an online gaming site, but don't expect that person to meet you for coffee.
Although virtual can be used to describe anything that exists in effect, but not in fact, it is often used to describe things created in a computer or online world. "She enjoyed playing the virtual role-playing game with her online friends." Virtual can also be used to mean "almost" — as in, "The blizzard brought the city to a virtual standstill, with subway and bus passengers stranded on the sidewalks."