The SD card expansion has the same effect as plugging in a USB drive and having access to another partition.
You can store files and media on there as well as programs if they are allowed to be installed in an external drive. You cannot actually move the operating system off the internal memory.
Having a high speed SD card will be better for accessing files and programs.
We have quite a few threads and posts on this forum regarding use of the SD cards and installing programs onto them that you can look at if you want to know more.
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