What actually happens to a refrigerator if it is laid on its side or back ? Is that a myth or does it ruin it?

,, well the oil inside the compressor with move around; then when the compressor is running... cant' compress liquid == damage compressor... damage or not depend how long it is stand up after it was laying on its side or back... I think the same thing also apply to room AC; I saw a lot of ac laying on their side

What caibuadday said.

Have I moved a fridge on its side? Yes, it was free and I had to put it on its side by my transportation availability and moving deadline. Did it ruin it? no.

can it do damage? My understanding is yes.

The oil in the compressor can flow into the cooling lines when the refrigerator is tipped onto its side. The oil may not completely drain from the cooling lines when tipped back up and the refrigerator may not cool.

You can try to avoid laying it completely flat by tipping it to an angle by placing a sturdy support under the top of the fridge to help keep the oil in the compressor. Also, there are several lines connected to the compressor. The cooling and discharge lines should be oriented to face up. You must keep the oil out of these lines. Laying the refrigerator over with the tubes facing up will minimize the risk of fouling the lines.

When you're done moving it, leave it upright for a few hours before plugging it in. This will give the oil an opportunity to flow back into the compressor.