PFC feature allows the MFS to handle the packet flow context : this is the qos context provided by GGSN at PDP context activation.
Thanks to the PFC, some MS could enjoy higher priority than other MS. When radio resources are congested, those MS will be served in priority.
In other words, there is a distinction between best effort and interactive class.
The Streaming feature comes ON TOP of the PFC. A thrid kind of MS is considered. Those MS would get a Guaranteed Bit Rate (GBR) and the highest priority.
Those 2 features are never used by operators, except in very few cases.
Because it adds a serious amount of complexity to a network, and those featuresmust also be activated in the core network (HLR/GGSN/SGSN)