In the UK there are 2 network levels in the electricity system: transmission and distribution.
The transmission system carries electricity at high voltages long distances across the country. It is run by the National Grid which is responsible for balancing the entire system and ensuring supply meets the second-by-second fluctuations in demand.
Then there are the distribution networks which take electricity from the transmission system and supply it to consumers (homes and businesses); shorter distances at lower voltages. Renewables are primarily connected to the distribution grid.