When an MP3 needs to become an OGG
What OGG Vorbis is
Vorbis was created by the Xiph.Org Foundation and reached version 1.0 in 2002. It is a lossy codec, like MP3, but open and royalty-free. The .ogg file extension normally means Vorbis audio inside an Ogg container.
Where you will meet it
Engines such as Godot and Unity read OGG, Android plays it, and many Linux players treat it as a first-class format. Spotify has also used Ogg Vorbis for streaming. That makes OGG a practical choice for game music and sound effects.
The lossy to lossy caveat
An MP3 is already compressed. Encoding it as Vorbis compresses it a second time, so a little more detail disappears. For background music and effects that is rarely noticeable. For critical listening, go back to the original recording.
Where OGG will not work
Apple devices, many car stereos and older MP3 players often skip OGG files. If the file is for other people, check how they will play it before you commit.
Game audio checklist
For looped music, test the loop point after converting, because encoding can add a few milliseconds of padding. Short effects usually need no further work.
Making game audio? Convert once from your best source file, name the OGG clearly, and keep the MP3 as a backup.