Below is a chart comparing the features of the different editions, under that is some further clarification:
Round Robins offer a different sampled version of the same sound each time you hit the same key, making each note sounds slightly different offering more realism.
BBC Discover contains no round robin samples, so there is only one sample per dynamic layer for each technique
BBC Core and Professional both include up to 8 round robins for added realism
Legato patches offer the most realistic playable sample sound available. These patches are monophonic meaning one note sounds at a time, if you play overlapping notes, you will hear the transition from one note to the other.
BBC Discover does not contain legato patches, Core and Professional do.
For each technique we record selection of levels for the instrument's dynamics (how loud or softly the instrument is played), very soft at pp through to loud ff
BBC Discover has 1 dynamic layer per technique.
BBC Core and Professional contain up to 3 dynamic layers.
Techniques - sometimes referring to as articulations - are unique sounds created by playing instruments in a certain way, such as Pizzicato (a plucked note) or Col Legno (playing a stringed instrument with the wood of the bow)
Discover contains 47 techniques
Core contains 305 techniques
Professional contains 435 techniques
For a full list of the included techniques please refer to the appendices in the user manuals or the "What's Included" list on the product page.