system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does putting a plastic bag or receipt paper over the magnetic strip of a debit card allow it to swipe easier?
gpt
A magnetic strip is just encoded data. So normally the card reader will read the distance between the "lines of the code" as you swipe it no problem. 

But if the card is scratched a card reader might see that scratch as an extra line or bit of code. [Rather the scratch isn't read as code, but read as incorrect code. The damaged code can't be read as well if there is more distance. This increases the chance that the correct information is read. (credit available_username2 below)]

The plastic bag or receipt increases the distance between the card reader and the magnetic strip. This is kind of like adjusting the focus on a camera. Too close and the card reader will read both the scratch and the legit code, but move the focus back a little and the card reader will only see the code.