[robski]

A Colour Space is a range of colours (gamut) bounded by a border.

sRGB is a device-independent color space ( think of it as an inter-connection colour Space ) based on "imaginary" primary colors ( think of it as a reference to a set of standard colours).

Input, output and monitor colour spaces are device-dependent (the range of colours that the hardware produces).

The idea of using the inter-connection colour Space is so that source device profiles to be constructed without knowing the actual destination device and destination device profiles to be constructed without knowing the actual source device.