Take a square wave with a duty cycle of 0<x<1, a frequency of f, and an amplitude of A. (The minimum value of this square wave is 0.) This signal can be decomposed into its frequency components by Fourier analysis. The frequency components of a signal are just the collection of sine waves that when added together give you the original signal.
In my line of work as a semiconductor test engineer, pseudo-random binary/bit sequences are very useful. They're random-ish streams of bits that can be easily and reliably reproduced using very simple hardware or software. Any semiconductor that can be used to transmit information can be tested at a functional level with a PRBS. Send a PRBS to the device you're testing, tell the device to repeat it back to you, and compare what you received to what you sent.
In my current role as a design verification engineer, I’m learning Verilog-AMS. I decided to make some notes as I go as a reference for myself. There may be errors in this document; I’m not a Verilog expert. This is just what I’ve gleaned from various online sources.