What are some examples of clades?
A clade is a group of organisms that evolved from a common ancestor. Eutheria is one mammalian clade and the other is Metatheria, which includes marsupials. The order primates can be considered a clade, as all members are descended from one common ancestor roughly that lived 60 million years ago. Another example of a clade could be birds: they all also descended from a common ancestor.
Check out this image from University of California Museum of Paleontology's Understanding Evolution series that will hopefully make things a bit more clear:
The bottom two images are not examples of clades because they exclude certain species or groups. Let's look at the orange example. If I trace my way back to the common ancestor (the very first line before it splits into two), I see that the line on the far right descends from this same common ancestor, but it is not included in the orange box meant to represent a clade. Thus, this is not a clade because the species on the far right is excluded.