Just to add, if you are connecting to an antenna, you will only receive ATSC-T channels and ONLY the ATSC-T tuner will be able to tune anything.
Also note that due to "must carry" laws, in the US, cable providers also transmit ATSC-T signals over the same coax cable as their ATSC-C signals. That means if you connect to your cable provider's coax cable, you will have access to both ATSC-T and ATSC-C channels (but not at the same time...).
(In other countries, cable providers may also provide terrestrial signals, but it is not required)
