This will let you monitor the FM broadcast band, television audio, and some government transmissions. However, use of wide band FM outside of the FM broadcast band and television channels is rare. A few scanners let you receive SSB as well, but SSB is seldom used above 30 MHz outside the ham radio bands, and even there narrow band FM heavily dominates. The importance of the specifications indicating a scanner's performances largely depends on where you live. The lower the number of microvolts, the weaker the signal that the scanner can detect and produce intelligible audio from.
Selectivity is measured in kHz for a certain level of interference rejection.
If you live in a rural area, good sensitivity is more important than good selectivity . With fewer stations to hear, you need to be able to catch weak signals and don't have to worry as much about interference. In a rural area, narrow band FM selectivity of 40 kHz at 50 dB will usually be adequate, while in an urban environment you will usually need selectivity of 30 kHz at 50 dB or better. Images are an unavoidable by-product of a scanner's circuitry, but the better scanners can reject most of these phantom signals and reduce their strength. Image rejection is how this is measured, and a good scanner should have image rejection of 50 dB or greater.