What is the difference between a “no fault grounds” and a “fault grounds” for divorce?

What is the difference between a “no fault grounds” and a “fault grounds” for divorce?

No Fault:
In a no fault divorce neither spouse has to prove that the other did wrongdoing, they just need to meet the mandatory separation period. For couples without minor children who have entered into separation agreements, this legal separation period is six months. For all other couples, the legal separation period is 12 months.

Fault Based:
Virginia recognizes three main reasons to file for a fault based divorce: adultery, cruelty and desertion/abandonment.