The artist credit concept is one of the many new changes that the next generation schema introduces. In the real world artists often work together on tracks and albums in various ways, but it is difficult to credit them. Not only this, but some artists have minor differences in the spelling of their name over different releases, and this information has been hard to capture in the past.
In the NGS server release we have implemented artist credits in places where the artist would have been credited previously. For example, the release artist and track artist fields now display artist credits. However, in conversation it is still perfectly acceptable to state "the release artist" or "what artist does that track have" instead of using the term artist credit.
Artist credits bring two main changes:
The first is the ability to link multiple artists to one release or recording, instead of having to create fake "collaboration artists". For example, the single "Under Pressure" had been credited to the fake artist of "Queen & David Bowie".
Artist credits solve this by instead linking the single to an artist credit that contains the two distinct artists, "Queen & David Bowie", and making it available from both artist's pages.
The second change is the ability to credit an artist with a different name. For example, the artist S.P.Y. can now be credited on a release with the name variation of "SPY".