Radio jammers exist. There is also special paint you can get that can keep wi-fi or other radio signals in or out. So if you have a wi-fi network at home but don’t want your neighbours of someone on the street to try to access it the paint will stop the signal getting out and it will stop interefering signals getting in. I think some art galleries/churches use it to stop people using cell phones in their buildings.
Radio/Signal jammers usually just fill the frequency with noise so that communication on that channel/frequency is not possible. They are usually indiscriminant and so it blocks everything in the set range rather than targetting a specific source.