Reverse-engineering is a term that is used for the process of taking apart something to figure out how to use it, basically.
In many cases, something new and great has come about from it. In order to understand how it works or to recreate it, engineers will pull it apart and study it.
The task that is difficult in reverse-engineering is the task of making what is in such a way that it will no longer be the same.
The fear that is involved has to do with the fact that patent information can be quite sensitive.
Copying a product that is under a patent is highly illegal. But, if they can figure out how to use it and make it in a different method, it may fall into the gray area.