From a mathematical viewpoint constants may represent factors that can not be determined. The number is inserted into the equation to get an answer. Constants may represent factors that cannot be detected because instruments are not accurate enough or factors that depend on the nature, or conditions, of space in a region. For example, some regions of space might have some type of energy field that humans have not previously encountered.
Physicists sometimes refer to the speed of light as constant, but every physicist knows the speed of light is not constant. The speed varies depending upon the nature of the medium through which light is passing. Certain artificially created situations may slow light. The speed is only constant in a vacuum, but space is not a true vacuum. Regions of space contain varying amounts of dust and gas which could affect the speed of light through the region.