Apple likes to hide the fuss of technical choices in its software. That includes Photos, which provides a lot of sophisticated functions with a friendly veneer. However, when it comes to exporting images, you might not know which option to take because so many choices appear quite similar.
To follow along, select any image in Photos. Now, in the File > Export menu, you see two options: Export 1 Photo and Export Unmodified Original for 1 Photo.