Can someone please clarify the below doubt?

We have two sequential activities A and B (they could be part of a complex PDM network diagram) with some dependency (SS, FF, SF) specified.  NO LAGS or LEADS are given.

1. SS relnship:  Means that B cannot start until A has started. Fine.   BUT does SS relnship also require that B must start at the same time as A, i.e., they start simultaneously?