Wide is used for the physical distance from one side of something to the other.
- We live in a very wide street. The car’s too wide for the garage.
Broad is mostly used in abstract expressions. Some examples:
- broad agreement ( = agreement on most points)
broad-minded ( = tolerant) broad daylight ( = full, bright daylight)
Broad is also used in the expression broad shoulders ( = wide strong shoulders), and in descriptions of landscape in a formal style.
- Across the broad valley, the mountains rose blue and mysterious.