C# syntax - Colon after a variable name -

quick question; I recently upgraded to VS2010, and received a new version of Reperaper.

Now, when Reperpar is giving me the full choice for one variable, then I'll variableName >:

: What is standing?

For example; I have this:

  var productIds = new list & lt; Int & gt; (InventoryItemsToProcess.Keys);  

And when I start typing a line like this:

var lastOrderDates = GetProductLastOrderDates (Pro

It gives me options for productIds and productIds:

What is the difference between the two?

The second is for C # 4.0 and here is one.