Keychain Access: "Click to lock the login keychain", what does that do?

[doxavita]

In the keychain access utility, at the top left is a lock, what happens if I click it? Is that safe to do?

Thanks

 

[angelwatt]

Perfectly safe. Locking a keychain simply means that if a program requests a password from that keychain (such as Safari or Mail), you'll be prompted for your login password to unlock the keychain before the application gains access to the password.