There is rarely a distinction made between the following 2 terms, but I think it's useful to separate the concepts of simple and easy.
There's an element of subjectivity to both definitions, but not enough of one to be a problem when distinguishing them.
Simple things simply lack complexity. That doesn't mean they're easy. For example, to find all occurrences of some item in the list that has no special properties that you can exploit is extremely simple. Just look at every item. But if that list is a few billion elements long, most people would not call that easy.
Simple and difficult problems are one that tend to require a lot of brute forcing.
Simple and easy problems are trivial.
Complicated and easy problems are poorly stated, One of the solution basically boiled down to "if you make this lucky guess, the rest is really easy". I hate those kinds of problems.
Complicated and difficult problems tend to be some combination of poorly stated, poorly understood, or just unapproachable with current tools.