Quoted Directly from Ev3lessons.com – “Introduction”  All credit goes to them.

Used here strictly for my students.

PROJECTS VS. PROGRAMS
• You will start by creating a PROJECT which has a .ev3 extension. You
change the name of a project by using the Save Project As option from the
File menu.
• You will write many PROGRAMS as part of each PROJECT file. You change
the name of a program within a project by doubling clicking on the program’s
tab and typing in a new name.
• Note: If there is an * next to the project name, you have made changes to
the project and you have not yet saved yet.
• There is a “x” next to project and program names. Clicking on it simply
closes the file (it does not get deleted).
Here are some common file extensions in the EV3:
• Programs (.ev3p)
• Images (.rgf)
• Sounds (.rsf)
• Text (.rtf)
• Projects (.ev3) – the only type of file you can open with the EV3 software
• Import file (.ev3s) – can be imported by an EV3 project