These two formats are identical file formats. There is absolutely no difference between a .jpg image and a .jpeg image — both formats apply the identical JPEG compression standard and save image data in the same way.
The difference is purely in the suffix, as it is a relic from the early days of computing. JPEG was developed in 1992 by the Joint Photographic Experts Group. When Microsoft introduced early versions of Windows, the system imposed a limitation: extensions had to be 3 characters.
This forced the 4-character .jpeg suffix to be shortened to .jpg for Windows users. Non-Windows systems, without this more info extension limitation, used the full .jpeg file extension from the start.
While both file types function the same in virtually all today's programs, there are specific scenarios in which a platform might need the .jpeg extension. When this happens, changing the extension from .jpg to .jpeg is enough.
No real file conversion is needed — only changing the extension fixes the compatibility concern usually.
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