For example, if a btc transfer was made for me from a wallet that does not use an description, I would see the description part blank in my wallet.
Or if I had made a transfer to a wallet that did not use an description by writing an description from my electrum wallet, electrum would not be able to convey this description?
Electrum does not share descriptions. It keeps them in the wallet on your computer where only you can see them.
How that happens?
With Electrum? Are you sure? I don't think so. I think maybe you are misunderstanding something.
There is an Electrum discussion sub-forum here at bitcointalk.org. You can try asking in there for a better explanation and access to experts.
You can find that sub-forum here:
https://bitcointalk.org/index.php?board=98.0