It’s the knowledge/wisdom that comes from the streets, with the act of experiencing things outside your bubble. One must walk, alone or with somebody, to know the extent of reality.
A man must not only be wise, but know how things work in practical means.

knowledge that you need to walk on the street of life; your experience, awareness etc

Street knowledge- a term for knowing the ropes of the street, and the to dos and what not to dos.