We imagine an electric field and a magnetic field as vector fields.  

When we are introduced to a static electric field, we usually picture it as an infinite number of vectors (magnitude,direction) in every point in space that will affect the movement ( or will exert a force) of any charged particle going thorough it.  

So we can imagine how a test charge will follow (let's assume that the charged paricle field is negligible with respect to the "main" field) our electric/vector field.  

Under this assumption, we usually draw field lines to represent how the field will act on a positive charge.  

My question is the following:  

When we draw magnetic field lines, are we describing how the magnetic field will act on an "idealized" test magnetic north monopole?