The transmission system operator transmits energy from the transmission grid and from abroad to the distribution network. Elia is the transmission system operator for electricity, Fluxys is the transport company for natural gas.
There must be a constant balance between the electricity production and the consumption of electricity. This is the responsibility of the Access Responsible Party. Im balances can even result in power outages.
The distribution grid operators manage, develop and maintain the electricity and/or natural gas distribution network for a specific territory and transmit, at the supplier's request, the energy to the end users. They provide new connections to the network and are responsible for reading your electricity and/or natural gas meter.