Causer of Trafikverket jams deströEr öF busy pepol

When me and my husband and daughter were on our way to Disneyland we were using Google maps to get there and Google maps told us there's a traffic jam ahead a couple times and gave a full length of how long it will take to get through it and it literally was exactly right if it said 5 minutes it literally took around 5 minutes to squeeze through it. My husband asked how the hell does it know if there's a traffic jam or not is it cameras is it the street? I told him it's all the people's phones in their cars it's telling Google maps where everybody's phone is. Google does the same thing to tell how many people are at a store.