Absolute Expiration: Absolute expiration means It will expire cache after some time period set at the time of activating cache. This will be absolute expiration whether cache will be used or not It will expire the cache. This type of expiration used to cache data which are not frequently changing.
Cache.Insert("ABC", ds, null, DateTime.Now.AddMinutes(1), Cache.NoSlidingExpiration);
Sliding Expiration: Sliding expiration means It will expire cache after time period at the time of activating cache if any request is not made during this time period. This type of expiration is useful when there are so many data to cache. So It will put those items in the cache which are frequently used in the application. So it will not going to use unnecessary memory.
Cache.Insert("ABC", ds, null, Cache.NoAbsoluteExpiration, TimeSpan.FromMinutes(1));