What is Verilog and how is it used in VLSI design?

Verilog is a hardware description language (HDL) for modeling digital circuits at multiple abstraction levels: behavioral (algorithms), RTL (register transfers), and gate-level (structural). Key constructs: modules (design units), always blocks (sequential/combinational logic), assign statements (continuous assignments), and wire/reg data types. Uses include: RTL design (synthesizable code), testbench development (simulation), gate-level simulation, and formal verification. SystemVerilog extends Verilog with advanced verification features (classes, assertions, coverage).