TV stations in the U.S. have switched from analog to digital transmissions and as such it is important that you have the right antenna for your TV setup and location. Whilst Analogue antennas can still provide a signal for your TV they are not optimized for the transmission frequency currently in place.
It is important that your antenna is able to receive both VHF channels (channels 2 – 13) and UHF channels (channels 14 – 51) in order for you to be able to view all TV content currently available. Many antennas specialize in one frequency range versus the other so it’s important to know whether you need channels in all ranges versus specific ones such as HDTV movies.
Here’s a link to the government communications site explaining in more detail the frequency bands and types of antennas that may be suitable for you.