When an interdiction field has been raised in a space system it means no ships are able to hyperspace out of the system. Even the ship that has raised the field is unable to leave. In the mud, if you move further than 10000 units away from the ship that has raised the field, you are able to hyperspace again.
The bridge commands to operate the field are <activate field> and <deactivate field>.
If you are in an interdiction field, you will be notified automatically when scanning the system.