Controller Area Network (CAN) is a slow (up to 1Mbit/s) serial communications protocol which was developed by Bosch in 1991, mainly for automotive, but now widely used in marine (NMEA2000), industrial, and medical applications. More information on the CAN network protocol family PF_CAN is contained in <Documentation/networking/can.txt>. If you want CAN support you should say Y here and also to the specific driver for your controller(s) below.
The raw CAN protocol option offers access to the CAN bus via the BSD socket API. You probably want to use the raw socket in most cases where no higher level protocol is being used. The raw socket has several filter options e.g. ID masking / error frames. To receive/send raw CAN messages, use AF_CAN with protocol CAN_RAW.
The Broadcast Manager offers content filtering, timeout monitoring, sending of RTR frames, and cyclic CAN messages without permanent user interaction. The BCM can be 'programmed' via the BSD socket API and informs you on demand e.g. only on content updates / timeouts. You probably want to use the bcm socket in most cases where cyclic CAN messages are used on the bus (e.g. in automotive environments). To use the Broadcast Manager, use AF_CAN with protocol CAN_BCM.