What does realism mean in international relations?

According to an article published on the official
website of Mount Holyoke College which is

a private liberal art college in South Hadley,
Massachusetts, Realism is an approach to the

study and practice of international politics.

It emphasizes the role of the nations and
makes a broad assumption that all nations

are motivated by national interests, or, at
best, national interests disguised as moral

concerns.