Start with these links then read the stuff below.
"Second Life is an online virtual world developed by Linden Lab. It was launched on June 23, 2003. A number of free client programs, or Viewers, enable Second Life users, called Residents, to interact with each other through avatars. Residents can explore the world (known as the grid), meet other residents, socialize, participate in individual and group activities, and create and trade virtual property and services with one another. Second Life is intended for people aged 16 and over, and as of 2011 has about one million active users."From me:
"Hi. I appreciate your kind offer of friendship, but I prefer to wait until I've actually met and spoken with someone before adding them to my Friends List. An alternative to "Friending" someone is to "Follow" them. I welcome "Followers." The button for that is on the right next to "Add Friend" on your Feed profile. Best wishes to you in your Second Life adventures! Maybe I will see you inworld one day. Until then... enjoy!"