The IP20 open-type enclosure means it's meant for installation inside a cabinet where it's protected from direct dust and moisture.
The normal-use current of 3.3 A is what you'll size the motor branch circuit for in a typical variable-torque application (fan/pump). The heavy-duty current of 2.6 A is the number to use when the load demands constant torque or short-term overloads — that's where the drive's thermal capacity is stretched. The light-overload rating of 3.1 A sits between the two and covers applications with moderate overload profiles.