Here's another analogy. DIGITAL radio is very much like Magic Jack or Vonage phone services. ANALOG radio is like Plain Old Telephone System dial up.
That said, there are basically two versions of ANALOG radio, AM and FM which dictate how the audio is modulated with the carrier. AM is usually used only on the aircraft bands, and FM is used everywhere else. Because of increasing channel congestion (think parking lot running out of spaces), the FCC has mandated that most FM services narrow their bandwidth (make the parking spaces smaller). Some have gone to narrow band FM (NBFM) while others have gone DIGITAL.
Unlike analog FM, there are multiple digital standards, and none are cross-compatible. Many law enforcement agencies have gone to the P25 digital mode, which "digital capable" scanners can decode. Other digital modes such as NXDN, MOTOTRBO and OPEN SKY can't be decoded by scanners.