What are Signal Diodes ? How are they different from Power Diodes ?

Signal Diodes are similar in working to Power Diodes. They are also PN junction Diodes. The difference lies in their capacity and frequency operating range.  Signal diodes have low power and current rating.  

They can function better in high frequency applications and are used in switching and clipping circuits.  

Signal Diodes are have a red or black band on one end which indicates the cathode.