I've lent a question and modified it for my very own reasons, however i can't stand carrying this out when I'm not entirely sure what it's doing. SQL paperwork are under descriptive about this clause. Here's what I lent and modified, do you know me what it's doing essentially?

(SELECT Id FROM
    (
        SELECT 
            Id
            ,RANK() OVER ( PARTITION BY DropStatusId ORDER BY StatusDate DESC) [Rank] 
        FROM 
            [dbo].[tblLHTrackingHistory] [TempHistory]
        WHERE 
            [TempHistory].[DropStatusId] = [DropStatus].[Id]
    ) [TT1] WHERE [Rank] = 1
)

The OVER clause means you are using statistics (versus say aggregates). Per the OVER documentation:

Determines the partitioning and ordering from the rowset prior to the connected window function is used.

Unlike aggregates, statistics do not require a GROUP BY to become defined.

Great solutions to date.
A visual example helps:

DropStatusId  StatusDate  Rank  
1             2010-02-19  1    <
1             2010-02-18  2
1             2010-02-17  3
2             2010-02-18  1    <
2             2010-02-15  2
2             2010-02-13  3
2             2010-02-12  4

The "partition" may be the records for any given DropStatusId.

Read this, it's pretty straight-forward. "Credit to Shaun Cruz"