You can simulate a synthesized netlist to verify that the synthesized design meets the functional requirements and behaves as expected. Although it is not typical, you can perform timing simulation with estimated timing numbers at this simulation point.
The functional simulation netlist is a hierarchical, folded netlist expanded to the primitive module and entity level; the lowest level of hierarchy consists of primitives and macro primitives.
These primitives are contained in the UNISIMS_VER library for Verilog, and the UNISIM library for VHDL.