this is glblb.v i dont get it

glbl.v

`ifndef GLBL
`define GLBL
`timescale  1 ps / 1 ps

module glbl ();

    parameter ROC_WIDTH = 100000;
    parameter TOC_WIDTH = 0;
    parameter GRES_WIDTH = 10000;
    parameter GRES_START = 10000;

//--------   STARTUP Globals --------------
    wire GSR;
    wire GTS;
    wire GWE;
    wire PRLD;
    wire GRESTORE;
    tri1 p_up_tmp;
    tri (weak1, strong0) PLL_LOCKG = p_up_tmp;

    wire PROGB_GLBL;
    wire CCLKO_GLBL;
    wire FCSBO_GLBL;
    wire [3:0] DO_GLBL;
    wire [3:0] DI_GLBL;
   
    reg GSR_int;
    reg GTS_int;
    reg PRLD_int;
    reg GRESTORE_int;

//--------   JTAG Globals --------------
    wire JTAG_TDO_GLBL;
    wire JTAG_TCK_GLBL;
    wire JTAG_TDI_GLBL;
    wire JTAG_TMS_GLBL;
    wire JTAG_TRST_GLBL;

    reg JTAG_CAPTURE_GLBL;
    reg JTAG_RESET_GLBL;
    reg JTAG_SHIFT_GLBL;
    reg JTAG_UPDATE_GLBL;
    reg JTAG_RUNTEST_GLBL;

    reg JTAG_SEL1_GLBL = 0;
    reg JTAG_SEL2_GLBL = 0 ;
    reg JTAG_SEL3_GLBL = 0;
    reg JTAG_SEL4_GLBL = 0;

    reg JTAG_USER_TDO1_GLBL = 1'bz;
    reg JTAG_USER_TDO2_GLBL = 1'bz;
    reg JTAG_USER_TDO3_GLBL = 1'bz;
    reg JTAG_USER_TDO4_GLBL = 1'bz;

    assign (strong1, weak0) GSR = GSR_int;
    assign (strong1, weak0) GTS = GTS_int;
    assign (weak1, weak0) PRLD = PRLD_int;
    assign (strong1, weak0) GRESTORE = GRESTORE_int;

    initial begin
	GSR_int = 1'b1;
	PRLD_int = 1'b1;
	#(ROC_WIDTH)
	GSR_int = 1'b0;
	PRLD_int = 1'b0;
    end

    initial begin
	GTS_int = 1'b1;
	#(TOC_WIDTH)
	GTS_int = 1'b0;
    end

    initial begin 
	GRESTORE_int = 1'b0;
	#(GRES_START);
	GRESTORE_int = 1'b1;
	#(GRES_WIDTH);
	GRESTORE_int = 1'b0;
    end

endmodule
`endif