What is the different between 1 count and 1 cycle in term of encoder signal?
Typically a "cycle" represents the number of cycles the electronics make per revolution of the encoder, a cycle typically defined by a single line on the encoder wheel passing through the sensor. So if there are 500 lines on the encoder, you will get 500 cycles per revolution.
Counts per revolution depends on counts per cycles. A typical encoder will have 4 counts per cycle. Counts meaning edges in the quadrature 00, 01, 11, 10 sense. Given a typical 500 line (cycle) encoder wheel, there will be 2000 counts per revolution.
I have worked with encoders where there were thousands of lines in the encoder wheel, with 40 counts per line, so over 100,000 counts per revolution.