Projects
In IntelliJ IDEA, a project helps you to organize your source code, tests, libraries that you use, build instructions, and your personal settings in a single unit.

Switch between projects
If you have several opened projects at the same time, you can switch between them using the following options:
Switch to the next project window: Ctrl+Alt+] (
)Switch to the previous project window: Ctrl+Alt+[ (
)
Alternatively, open the Window menu and select the project to which you want to switch.
Project formats
In IntelliJ IDEA, there are two types of formats in which a project's configuration can be stored — the file-based format and the directory-based format.
File-based format
The file-based format was the only one available in older versions of IntelliJ IDEA; now it is outdated. Projects in this format contain several files: the .ipr, .iws, and .iml files. Generally, we don't recommend using this format unless you need to open projects in different file managers by clicking the .ipr file, or unless you need to store multiple projects in one directory.

Directory-based format
For the directory-based format, the IDE creates the .iml file and the .idea directory that keeps project settings. It's the default format for projects in IntelliJ IDEA at this moment.
This format was introduced after the file-based format. Its main advantage is that it's adjusted to store project files in Version Control Systems: the project data is split over multiple files, and merge conflicts are less likely. For more information on how to share projects in different formats, refer to How to manage projects under Version Control Systems

Change the project format to directory-based
From the main menu, select
.
Change project location
Move a project to another location
In the Project tool window Alt+1, right-click the root directory of your project and select (F6).
In the dialog that opens, specify a new location for the project and click Refactor.
Change the default location for projects
In the Settings/Preferences dialog Ctrl+Alt+S, select .
In the Default directory field, specify the path to the folder in which you want to store your projects.
Apply the changes and close the dialog.
Share project settings through VCS

List of non-shareable configuration files
IntelliJ IDEA identifies configuration files and adds them to the list of ignored files automatically. However, if you are sharing your project manually, we recommend that you avoid placing these files and folders under version control:
- .idea/workspace.xml
- .idea/tasks.xml
- .idea/usage.statistics.xml
.idea/dictionaries folder
.idea/shelf folder
.idea/libraries if they are generated from Gradle and Maven projects
*.iml and .idea/modules.xml files in Maven and Gradle projects
- gradle.xml
*.iws file in file-based projects
out folder
For the full list of files, refer to How to manage projects under Version Control Systems and JetBrains.gitignore.