The IPAF training categories, with abbreviations and brief explanations, are:

Static Vertical (1a): Vertical personnel platforms (static)

Static Boom (1b, 1b+): Self-propelled booms (outriggers), trailers/push-arounds, vehicle-mounted platforms

Mobile Vertical (3a, 3a+): Scissor lifts, vertical personnel platforms (mobile)

Mobile Boom (3b, 3b+): Self-propelled booms

Push Around Vertical (PAV): Push around verticals

Special (SPECIAL): Specialist machines

Mast Climbing Work Platforms (MCWP) 

Insulated Aerial Devices (IAD) 

Harness Use and Inspection (H)

Loading and Unloading (LOAD)

MEWPs for Managers (MM)

Goods Hoist (GH)

Transport Platform (TPH)

Personnel Hoist (PH)

What the "+" symbol means
This means that the operator has successfully completed the PAL+ course, which covers additional, practical training and testing on the machine category indicated. The operator has successfully demonstrated his/her ability to operate powered access equipment safely and effectively in challenging work environments.