LVM question: what's the difference between /dev/mapper/vg-lv and /dev/vg/lv

[yudi v]

I created a LV and was going to use the following command to create a file
system:

mkfs.ext4 /dev/vg/lv

someone suggested I use:

mkfs.ext4 /dev/mapper/vg-lv


What's the difference?

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Kind regards,
Yudi