what is imperial units
The inch is the basis of the Imperial measures of length, and is now legally defined as exactly 2.54 centimetres. This means that the Imperial units of length are based on the metric system! If you want a quick conversion, then 2 inches is roughly 5 centimetres. To inch forwards means to move slowly forwards.
Imperial system of measurement, on the other hand refers to the system used in the British Empire in the 19th and 20th centuries. However, after adoption of metric system, Imperial system has been reduced to a few countries of the world, notably UK, and surprisingly US.