This is nothing but just a clock divider code.
If the input clock is 50MHz, then the output will be 1Hz,
means its a divide by 50,000,000.
But there are mistakes here
1. If you really want 1Hz, then you should give 24999999, instead of 25000000, because the counter includes the zero, or you can put the less than (< ) operator instead of equal to (==)
2. You should specify the base of the counter, means the base should be decimal. Other wise count will change, i think default it will take it as hexadecimal (i don't remember the default base), so here you can put 25'd2500000 or 25'd24999999.