Ok, the title is surely not good to explain my very basic question, but here it is:

I just started creating a wordpress theme and the index.php has two columns:

1.) The main content and

2.) A vertical column where I am showing other info like Archives, Recent posts all programatically.

**Updated**

Until now everything was fine then I heared about registering a sidebar that shows some content other than the main content(which **I think** sounds to me very similar to mine). Is this sidebar a functionality provided by wordpress itself or it has to do something with my theme's sidebar(which was created by me)? Also is a sidebar is necessary to be registered for a theme? Do I need to do something to register my sidebar and if yes what exactly? 

Also what exactly does it mean(I mean what happens behind the scenes in terms of DB or or other sql queries) to register a sidebar in a theme?