Resin-coated - In order to speed up machine processing, the materials manufactures developed a "plastic coated" paper which has become almost universal during the past 50 years in spite of the fact that it can be very unstable. The emulsion is sitting on top of the "plastic" rather than being embedded in the paper so it is subject to many problems that make the life expectancy nearly impossible to predict. You can find a lot of information on the subject if you go to the Agfa or Kodak web sites.
Your question brings up an interesting thought - maybe Doug can be talked into adding a Glossary of Photographic Terms to the web site. Some people are afraid to ask - I'm glad you were not! :-) How about it Doug?