Here you are
Definition 1 of 2
Pro Tip 1/3Offering Items
Used when physically handing over an item to someone else. 
Here's the book you wanted to borrow, here you are.
Pro Tip 2/3Politeness
Often used to show politeness, especially in service situations. 
After packing your groceries, the cashier might say, 'Here you are.'
Pro Tip 3/3Completing Tasks
Signals completion of a task or fulfillment of a request. 
I've finished fixing your bike, here you are.