I used Eclipse for about 5 years and have now been using IntelliJ for about one year. I eventually came to the conclusion that what IntelliJ calls a "project" is basically what Eclipse calls a "workspace", and what Eclipse calls a "project" is basically what IntelliJ calls a "module".
This can cause confusion to start with, because you tell IntelliJ that you want to add a new "Maven project", which IntelliJ understands to mean you want to add a new "Maven workspace" in Eclipse terminology. So what you really need to tell IntelliJ to do is to create a new module (aka equivalent of an Eclipse project) in the workspace (IntelliJ project).
Because we come from an Eclipse background, most of us just refer to IntelliJ projects as "workspaces" in my organisation, and explicitly qualify "IntelliJ project" if we need to use the word "project". I think this reduces confusion, because an "IntelliJ project" has a different scope from a "Maven project", unlike in Eclipse.