We are using AdventureWorksDW2008R2 database, simply check the any dimension table, let’s say DimProduct table.
Select ProductKey,ProductAlternateKey,EnglishProductName, StandardCost, ListPrice, DealerPrice,StartDate,EndDate
In this table we have two keys, Product Key and ProductAlternateKey, here ProductKey is Surrogate key and ProductAlternateKey is Business Key.
ProductAlternateKey uniquely identifies the product in our application, but over the period of time the rates have been changed of the product, and which rate is current rate is defined by EndDate, and to uniquely identify different state of product in the table we have ProductKey.
This concept is also known as Type 2 Slowly changing dimension concept, which saves historical state of Entity by inserting new records