A simple definition for frequency is a specific scientific measurement of how often something repeats per second.  On the other hand a simple definition for pitch is a perception of how high or low a sound is.   So whats the difference between the two?  Well not much really.  For example the frequency 1760 Hz is also the note A6, which could be described as the pitch.  When you hear the sound you aren't going to be able to say oh thats 1760 Hz, what you can say however is that the sound was very high or maybe even that the note was A6.