Infinite Horizons is a role-playing game (RPG). As with many areas in life, RPGs make regular use of various terms and acronyms, which this rulebook assumes you are familiar with. In case you are not, here are some introductory definitions. Other terms will be introduced, defined and acronymed where appropriate.
A role-playing game is a game of imagination, where the only limits are those you impose on yourself. Almost anything is possible (some things are just very, very improbable). RPGs require nothing but paper, pencil, and people (although preparation is important for some people and may contribute to everyone's enjoyment). Aids, such as miniatures, maps and costumes, can make things easier to visualize, but are by no means necessary.
At a minimum, two people are required in order to play, although there are frequently more. There must be a game master, and at least one player.
A player is an actual living, breathing, human being who will create and control a character. Most people begin their role-playing careers as players, as it is much easier to be a player than a gamemaster.
A character is an imaginary person (or creature). A character is not a real person, but they may seem real, if the player does their job well. Think of the player as being like an actor, and their character is the role the actor is portraying. There may be a group of characters called a party.
Players are not characters, and characters are not (necessarily) players. You may make a character that looks and acts just like you, but you don't have to. It is often more fun to make a character that is not at all like you, and then enjoy the challenge of trying to play your character the way he or she would act, not how you would act.
Remember that your character doesn't know everything that you know, and vice versa. Knowledge may, and probably will, overlap in some areas, but just because you know how to ride a horse or make nuclear bombs out of cotton balls and toilet bowl cleaner, does not mean that your character does. Of course, even if you don't know how to make nuclear bombs out of cotton balls and toilet bowl cleaner, your character may. Keeping player and character knowledge separate is possibly the hardest aspect of role-playing.
The game master (GM) is the person responsible for creating the situations that the players will find their characters in. These situations may be made up by the GM, or they may have been written by someone else. The GM will have much more knowledge about the surroundings than the players, and is responsible for describing the setting and determining what results the actions which the players select for their characters will have.
Characters controlled by the players are called player characters (PCs). This is because they are characters controlled by players. Characters controlled by the GM are called non-player characters (NPCs), because the GM is not considered a player. NPCs include all of the incidental characters that the PCs run into during their adventures, but can also include characters in the party. NPCs are often not defined as completely as PCs (the GM rarely needs to know in advance the complete character history of each shopkeeper, for instance).
Another important aspect of an RPG is the setting. The setting is the location where your game takes place. It may be very general (e.g. interstellar space), or it may be very specific (e.g. Wall Street).
As mentioned in the foreword, there will be supplements available for playing Infinite Horizons in different settings. These supplements will add some new setting-specific rules, but will mostly provide new character races, equipment, and skills to add to the existing appendices.
It is possible to play with just the information available in this book, but this consists of only the bare essentials, and the options available to you will be limited. Your enjoyment will be enhanced by adding the supplement (or supplements) you are interested in and using the rules contained therein.
A gathering of players and a GM for the purpose of playing an RPG is called a role-playing session. Sessions often last for several hours.
Often, a group of players and their GM will use the same set of characters in the same setting for several sessions in a row, for the purposes of achieving some goal or mission which is too time-consuming to complete in a single session. This is called a campaign. Campaigns can last just a few sessions, or can continue over years of both real- and game-time.
A campaign can take many forms. Most involve some sort of story in which the players participate as the main characters. (The characters might only be living a small part of some world-changing event, but in this part of the story, they will probably still be the main characters.) The GM plays the role of the story teller, much like an author writing a novel. However, the characters of this particular novel have minds of their own, and the story may not end up anywhere near where it was originally intended to go.