It is possible to select the fittings available in a number of different beam widths. There is always a trade off between the amount of light spread you get versus the intensity of the beam.
By selecting different beam widths for fittings you control the spread and dispersion of light.
Beam width is measured as the spread from one extent of the beam to the other.
The distribution of light will not usually be spread evenly across the beam, with the centre being brighter.
Varying your selected beam width can be very effective, for example: using a very narrow beam (c.8-15 degrees) to uplight a column or using a wide beam to create broad pools of soft light in living areas.
For general lighting, if you have very low ceilings you may want a broader beam width (c.45 degrees), and if you have very tall ceilings you may want to err on the side of using a narrower beam (c.20-24 degrees).