There are three main categories that describe how light is diffused into a room and the type of fitting you select will affect not only the quality of light but the way that it is directed into the room. Each of these categories is discussed in more detail below.
Indirect lighting is really self-explanatory being achieved with light fittings that do not shine light directly into the room itself. Instead, the light is reflected from another surface resulting usually in an even glare-free light. Uplighters are an obvious source of indirect lighting as they are usually positioned so that the light bounces off the ceiling and then is reflected back into the room. Desk lamps can also be used as a form of indirect lighting as they can be swivelled to reflect light off the wall in the evening whereas normally it would be used for task lighting and therefore would be considered a form of direct lighting.
Direct lighting is achieved by using light fittings which shine directly into the room. The large majority of light fittings fall into this category but some are adaptable depending on how they are used such as the case of the desk lamp referred to in the above paragraph. By simply adding a shade to a light fitting can alter the effect from direct to diffused lighting.