Bidirectional charging means that an electric car is not only able to take in electricity, but also to give it back again. The basic requirement for this is a suitable charging station and, when indicated, a bidirectional onboard charger. The electric car then acts as a temporary store for electricity that is currently not needed.
When the electricity is fed back into the power grid, it is called Vehicle-to-Grid (V2G). The car then becomes part of an intelligent power grid, in which it temporarily stores excess electricity from wind or solar systems, for example. This could prevent peak loads.
If the electricity is only used in one’s own house, it is referred to as Vehicle-to-Home (V2H). The electric car acts as a temporary storage for the electricity from the private photovoltaic system, for example.
The term Vehicle to Everything (V2X) covers all other possible scenarios.