Does every ram module fit every laptop?

I have a laptop and this ram is built into it.

https://www.ebay.de/...2332636641

It has 2 ram slots but only one of them is used.

Question: can I use another laptop ram or is that what I don't have?

Do both RAM cards have to be the same?

I'm sorry about my grammar and spelling mistakes.

In a nutshell:

as long as the design is correct, the rest is irrelevant,

the strong ram then adapts to the weaker one

https://www.alternate.de/Arbeitsspeicher/SO-DIMM

With RAM you have to be extremely careful. Even if a RAM bar has exactly the same manufacturer information as one that is compatible, that does not mean that it is also compatible. There are certain patterns among manufacturers (e.g. Corsair RAM often doesn't work in ThinkPads, but Crucial RAM does), but you can't say anything for sure about that.

Therefore, you should make sure as far as possible that the RAM is compatible with the exact laptop model or buy the already installed latch again.

It would be nice, but unfortunately that's not the case. RAM is the most idiosyncratic type of component that I know of. As long as you don't know for sure that a specific combination of RAM and laptop is compatible, you can only guess.

Yes, the RAM should of course also be supported by the mainboard, but pretty much every manufacturer has a list on their website.

the rest of the time it doesn't really matter whether there are 2 identical bars or not