"Stride frequency" refers to how quickly a person takes steps while walking or running. It measures how many steps they take in a given period of time, usually measured in steps per minute. Full definition
If you are interested in how your speed is affected by stride length and stride frequency then this article over at Science of Running is worth a read. (fitbodyhq.com)
These improvements included increases in running speed, right forelimb stride length, right forelimb maximal longitudinal deviation, and right rear stride frequency. (asteriasbiotherapeutics.com)
In addition, the iliopsoas (a hip flexor) seems to be very important for increasing speed through increases in stride frequency at speeds of > 7m / s (Dorn et al. 2012). (strengthandconditioningresearch.com)