This video published by Western Power distribution summarises it well
Distribution Network Operators (DNOs) have had the job of delivering electricity to customers since the privatisation of the electricity system. This job is changing as more homes and businesses generate their own power requiring energy to be transmitted both ways through the network. This creates new challenges that Distribution System operators (DSOs) have to address. DSOs have to have more real time data, from smart meters installed in homes and businesses, and intelligent controls across their networks. DSOs may also have to work more closely with other operators to balance demand between regions.
In the future customers could earn benefits from using energy at different times of the day, as part of future flexibility markets.
For example, a business that already generates some of its own electricity from solar panels could install a battery to store and then export power to the network when needed or a home could change when they charge an electric vehicle and shift their demand to off-peak periods. By having more visibility and control over power flows across their networks, DSOs can avoid costly upgrades and speed up connections for new customers ensuring a secure, low-carbon and affordable electricity network for all.