Question

what is a side by side feature

Answer 1

http://www.google.com/search?q=side+by+side+feature+computer&oq=side+by+side+feature+computer&aqs=chrome..69i57.5772j0j7&sourceid=chrome&es_sm=122&ie=UTF-8

Read lots and read carefully.

And here's an example of side-by-side versions of a work of literature: Shakespeare's English on the left, modern-day English on the right.
http://nfs.sparknotes.com/hamlet/page_40.html