how to display value of input in DIV object in real time

how to display value of input in DIV object in real time

Hello everyone,
I'm new in jQuery and have some (maybe idiotic) question.

F.e I have div which id is someDiv and input text which id is someInput - and how to do that value of input object will display in DIV in real time? If i type letter "a" in input, it should automatically display in DIV.
Which function should I use?
I'm the real begginer in jQuery.

Thank you in advance.