The 'bean' is the restriction in a choke valve. A choke is a constant pressure control valve, so that down stream pressure is separated form upstream pressure. Bean size is traditionally measured in 64ths of an inch, so if someone talks of a 32 choke, the hole is 32/64" in diameter, ie half an inch. Usinally the maximum bean size is limited by the size of the choke valve- if you have a 1 inch choke valve, you can't have more than a 64 bean in it!
Bigger bean, means bigger hole, means more production, (provided the flow through the choke is still in critical flow, ie the flow velocity through the choke is still greater than the sonic velocity).
Try the manufacturer's websites: Anson, Masterflo, for picture of choke valves etc.