What is the difference between kinetic energy and mass?
First, let's define energy; plain old vanilla energy.
Energy is a capability. It's a capability to do work or cause a change. In other words things that have energy can do work. Like if you have energy you can tidy up your room, which is doing work.
There are all sorts of energy sources. One of those sources is motion. A waterfall. for example, has the capability to do work (i.e., it has energy) because that water is in fact falling. It's moving. And when anything has the capability to do work because it's moving that capability is called kinetic energy.
Mass cannot do work or cause a change. It is not energy. So there's a major difference. One is energy the other is not. Mass at some level of quantity can be touched. It is tangible. Energy is not tangible; it's only a capability. Mass is a measure for the inertia of an object.
NOTE: You've probably read about E = mc^2 and the term mass.energy. Some interpret that as meaning mass is energy. It is not energy. It is the potential for producing energy, but it's not energy itself because mass cannot do work or cause a change.