How does the login names from one PC show up on a different PC?

[evady]

I have a weird question. One that I could not figure out how to word in Google to answer it.

I have 3 PC's on one router/modem setup. 2 of them are wired and one is wireless. Whenever someone uses the wireless one, the Login ID's show up on one of the wired PC's but not the other. So when logging into places like Facebook and Email accounts, the Login ID's are visible
on the other PC. Again only on one of the wired PC's not both. Does that make sense to anyone.
It's more of a curiosity than anything that could be potentially a privacy violation. It's only the Login ID's not passwords or anything like that.

[Jman]

If you use Google Chrome and have logged in to your account with it, that's what it is. If not, look at other answers.