Friends on profile

I get it now, cool. Thanks a bunch!

When you look at a profile, the icon next to the mail icon (a smiley face) i the friend icon. Press this and that profile is put in your friends section (fourth button on the left).

The person you friend does not know you friended them. This is just a shortcut to getting to those you want to keep track of.

Hey there, how does one become a friend on this website? I mean, are you chosen by another member? I have noticed that the smiley face icon on a members profile I have visited is highlighted/on and I do not know what that means. Does it mean I accidentally clicked on a button and friended them or they did me?
Please advise as I search on help and could not find an answer. Thanks