In the various phone, mobile and web services, there are contact lists that differ in name. In instant messaging( IM) and chatting, the contact list with corresponding data of friends is called: Buddy list.
In a buddy list, friends without and with photos are entered with whom one would like to keep in contact. The entries also show how and when the respective friend can best be reached. When the buddy list is called up, the user can see directly which friends are offline and online, which are currently having a conversation or can be contacted directly, or even which have switched off their smartphone.
When user "X" activates his instant messaging application, the messaging client establishes a connection to the messaging server where the user logs in. After that, the buddy list with all registered friends appears on the display.
The messaging serverchecks the buddy list and shows in the display of the user "X" which friend is ready for messages. At the same time, the server updates the buddy lists of the friends and shows in them that user "X" is currently available.