This could represent a service person (plumber, roofer, electrician...) coming to your house to do work. A set fee is charged just for showing up at your house. That is the "w".
And then say the plumber charges $6 per hour, and if he spends "b" hours at your house, then this would be the expression for how much it costs to have the plumber come and fix something at your house.
So if a service call costs $60, then $6 per hour for however long it takes the plumber to fix the problem, then you would pay 60 + 6b