DAM for Sitecore integrates the Digizuite™ asset management into Sitecore, allowing you to embed assets from Digizuite™ into your Sitecore website.
Although the Sitecore Media Library still exist in Sitecore, DAM for Sitecore should be seen as a replacement for the Sitecore Media Library.
If you have experience with DAM for Sitecore v3.x or v4.x, you will find that everything has changed. DAM for Sitecore v8 is rebuilt from the ground and up. This has been done to meet demands of the two worlds DAM and Sitecore and to create a much stronger and deeper integration.