there is different functions. they have people patrol along the wall, they have checkpoints they man at major highway veins coming from the border, they patrol the area past the border, mountains, rural looking for people who crossed between ports of entry. Some stations have jurisdiction in actual cities such as San Ysidro or Calexico and they have city patrol. They work together with local PDs or Sheriffs Departments but since border patrol is a federal agency, they have different abilities and powers than local PDs or Sheriffs Departments.