Answer:
The North or Union had more supplies, and land. The Union, also had a larger population, and they could draft/conscript regulars into the army. The south, on the other hand, had a limited army. The Union was also mainly industrialized, unlike the South, which was mainly agricultural.
The South had more experienced officers and generals, which meant they could fend off a Union invasion even if they were outnumbered. At the end, however, even if the South had better experienced officers and generals, they wouldn't have enough men to fight off the giant Union army.
