The term "LPS" is one that hobbyist use to describe large polyp stony corals. This group of corals is often thought of as having a more fleshy appearance and larger more visible polyps than "SPS". Some would say that these corals require more feeding than SPS, but this is a gross generalization that does not always ring true.
"Stock corals" means what is for sale may not be the exact items pictured, but clones similar in appearance. There may be some "What You See Is What You Get" items listed here as well which will have "WYSIWYG" in their title.