A network effect happens when the value of a product increases as more people use it; like with social apps.

A congestion effect happens when the value of a product decreas$$s as more people use it$,$ like with too many people trying to stream data on wi$-$fi that has limited bandwidth.

A social app like Instagram becomes more valuable to existing users as more new people join.

The user experience of driving on a crowded highway corresponds to the network effect, the value of it increases as more people decide to drive on it$.$