what is "deauthentication?"

Question

So if authentication is validating usernames and passwords with an ip address, what is "deauthentication?" I look on google and I don't get the concept of deauthentication. I think its like verifying disconnection when logging off of wifi, website, etc. which would explain wikipedia's definition of a "deauthentication attack."

I say this because I was using the wifi pineapple mark 5 trying to get usernames and passwords from my target computer (the one I use as a target that I also own) for wifi. So I thought it would be helpful to understand my options. I'll screen shot if you need to see where I got this question from.

Answer 1

Deauthentication occurs when a router tells a (Wi-Fi) client to disconnect from it.

Spoofing deauthentication packets causes the targeted client to lose connectivity so it then needs to authenticate to an access point again, which means sending the login credentials.