There are two kinds of resources for an army. There are material resources and there are less tangible resources. At the beginning of the Civil War, the Union had much more in the way of material resources but less in the way of intangibles.
In material resources, the Union had more of everything. They had more men. They had more weapons and clothing and blankets. They had more factories to provide more of these things as needed. This was a huge advantage. By contrast, the South's main advantage was in the fact that it had the bulk of the professional soldiers. Its officers were better trained than the Union officers. More Southerners were used to riding horses and to shooting guns. These less tangible resources helped to make up for the deficit in material resources.