So cyberspace lets us communicate and share information with each other. If that were all, we would hardly call it a space. But, cyberspace is a two-way thing: like the real world, we are affected by cyberspace and affect it. It contains 'virtual worlds'. For example, the Internet can be used for showing TV pictures - a one-way process. Just as we might imagine ourselves into a TV film, we can imagine ourselves into a cyberspace 'film'. But more, we can interact with other people also imagining themselves into the story, and now the process becomes two-way. We begin to get a sense of a 'virtual world'. There are a huge range of virtual worlds in cyberspace: some are realistic three-dimensional worlds, and others are rather more like the imaginary worlds we create in our heads when we read a novel - based almost entirely on text. Some virtual worlds are games, and they can be very addictive games, often involving role-playing where the players are fantasy heroes (generally with magical and spiritual overtones). Some virtual worlds are quite literally serious business, as when a worldwide company wants to run a high-level conference.
Internet Relay Chat (IRC) is a very popular form of virtual world. It is quite cheap and accessible - it only uses text, and therefore relies more on people's imagination. So, IRC is more like a conference telephone call than a shared TV experience. With IRC, chat rooms are created where people can drop in and discuss whatever they like. Sometimes, some of the participants in chat rooms will actually be computers, with their own characters. Some chat rooms are used for role-playing games (like the fantasy game Dungeons and Dragons); these are often called MUDs, or Multi-User Dungeons.
From the human perspective, a virtual world becomes virtual reality when we cannot tell or are no longer concerned about the difference between it and reality. Long ago, when a lion jumped out at you, you wouldn't stop and think whether it was a picture or not - you'd run, or pray, or probably both! If something looked like a lion, it was a lion, and your survival would have depended on your never pausing to worry about the difference. Now images in virtual reality hit our senses as if they were real. Provided we don't look beyond the edge of the screen, the images landing on our retinas are very close to real images. In other words, virtual reality is real as far as our emotional reactions and our instant responses are concerned.
The power of this virtual reality is enormous. People can be trained to fly aircraft without any of the physical dangers of flying (or firing missiles at the wrong targets); and at the other end of the spectrum, cyberspace can create sexual fantasies that are 'real' without any of the responsibilities required in reality. There are commercial products to support each of these applications. Many fear that people will immerse themselves in false models of the world, intentionally or otherwise, when what is needed is action in society and the environment to sustain life.