A boulevard is a type of street. You can get to school by taking the four-lane boulevard, but to avoid all the traffic, you might use the less-traveled side streets.
A boulevard is a street or avenue, especially one that's very wide and lined with trees. Many boulevards have a median strip of grass and sometimes trees. Boulevard strip is the regional term for a patch of grass between a curb and a sidewalk, which in other places is called a tree lawn. The French word boulevard literally means "rampart," or "defensive embankment." Later it was adapted to mean "a promenade beside a rampart."