All 3 of my sd cards say error after filming videos with them. What did I do wrong?

All 3 of my sd cards say error after filming videos with them. What did I do wrong?
This minute
I have a Samsung NX10. I started filming videos on the first card. (in 16:9 resolutionand hq quality. Some of the videos were large. I would delete them on the camera and on the computer.

It was fine for a bit. Then the camera said error and the card wouldn't show up on the laptop. So then I use another SD that said hd video. Same thing happens eventually.

What am I doing wrong? I thought you just put an sd card in the camera and that was it. Apparently you need to reformat things? How and why?

I would like to recover the pictures on the one SD card. But I also want to make all 3 cards unsuable again. How do I do this? I know nothing about these things, so explain like i'm really dumb.

If I need to download something, I will.

help please.

Read more: All 3 of my sd cards say error after filming videos with them. What did I do wrong?