Display Suite gives you full control over the way content is displayed without having to maintain dozens of PHP template files. We can accomplish this by using a drag and drop interface to arrange the display of fields in predefined or custom regions such as as "header", "left", "middle" or "footer".
Display Suite comes with predefined layouts such as "two columns", "three columns stacked", "three columns fluid" et cetera, but also lets you define your own ("nine columns stacked" anyone?)
Display Suite takes over the Drupal core functionality that let you arrange the display of entity fields via the "Manage display” tab.
You can manage the display for each "view mode" such as the full node, teaser, search result or your custom view mode (e.g. "mini teaser"). The Display Suite view modes are available in Views so that you can efficiently create & maintain lists of content.
Display Suite allows you to add fields to the node, user or comment varying from a simple piece of html (e.g., social services links) to preprocess fields that you define in a theme or module.
For each field Display Suite lets you define how the field and its label are formatted (e.g., as plain text or as a link, inline or above) and which markup to use (e.g., "H2, div, p"). On top of that you can define css classes for fields and easily change the value of the label using field templates.
For Drupal 6 you need various modules, in Drupal 7 these are combined into one module. Version 7.x-2.x introduces many changes compared to 7.x-1.x.