What are the differences between SIMULATION and SYNTHESIS

Simulation <= verify your design.

synthesis <= Check for your timing

Simulation is used to verify functionality of the circuit.. a) Functional Simulation:study of ckt's operation independent of gate delays and timing parameters. b) Timing Simulation :study including estimated delays, verify setup, hold and other timing requirements of devices such as flip flops are met.

Synthesis: One of the foremost in back end steps where by synthesizing is nothing however converting VHDL or VERILOG description to a set of primitives(equations as in CPLD) or components(as in FPGA'S)to fit into target technology.Essentially the synthesis tools convert design description into components or equations.