Yes, depending on how you would like connectivity established between the features in your network. When you select Yes to snapping in the Build Geometric Network wizard, you’re selecting the feature classes whose features you want to be moved.
If your junctions are coincident with the end points of simple or complex edge features, connectivity will be established regardless of whether you choose to perform snapping or not.
For junctions located at mid-span along an edge feature, connectivity is established depending on whether the junction is snapping to a simple or complex edge.
Connectivity is never established along mid-span of simple edges. Even if your junction is coincident with a vertex, or located along a simple edge, no connectivity is established.
With complex edges, connectivity can be established at mid-span when the junction is coincident with a vertex or located along the complex edge. By default, when snapping is not selected, connectivity will only be established between the complex edge and junctions that are coincident with vertices along the length of the edge. In order to establish connectivity between junctions and complex edges, when a vertex is not within the snapping tolerance, you must perform snapping and select the complex edge feature class for snapping.