I need to know what a vacuum hose is and where to look in my 1999 cheverler G3500 express cutaway truck

I have a cheverlet G3500 expressway truck. MY brake on the back passenger side is locking, My check engine light comes on, and the power steering just went out. I entried all these problems in AutoMD and each one can be related to the vacuum hoses. But I don't know where or what a vacuum hose look like. Can some one show me or direct me to where and what the vacuum hose is?