Sorry, totally new to this wireless network thing, but with have just got a new laptop in the office with wireless network card...

How do you log on to someone else's wireless network?

When I enable the wireless, I can see 4 other wireless networks in my locallity. If it try to connect to them it asks for username and password. Are these "protected" then?
Would an unprotected one just let me login without asking for authorisation?

steve