Understanding the Highway Code is essential when using public roadways.
It is not just limited to common road users such as cars, bikes and large vehicles. It actually covers everything from pedestrians to horses; mobility scooters to road sweepers.
It is considered as instructions on how to use public roadways.
You can get a free copy of the highway code from https://www.gov.uk/guidance/the-highway-code
If you prefer a paper form you can also buy it here.