Help with UVM coding

[promach]

Could anyone help to explain what the following uvm coding does and how it works ?

module m;
  `include "uvm_macros.svh"
     import uvm_pkg::*;
bit clk;
bit[3:0] a=4, b=5, c;
initial forever #10 clk=!clk; 
 
always_comb begin
    for (int i=0; i<=3; i++) begin
      assert(a[i] > b[i]) else $display("i a[i] b[i]", i, a[i], b[i]);         ap_ab: assert property(@ (posedge clk) a[i] |=> b[i]); 
    end   
end
        initial begin
         repeat(20) begin
             @(posedge clk);   
             if (!randomize(a, b)  with
             { a dist {1'b1:=1, 1'b0:=1};
               b dist {1'b1:=1, 1'b0:=2}; 
         }) `uvm_error("MYERR", "This is a randomize error");
         end
         $finish;
        end 
        
endmodule