Realpolitik: This is a system of politics based on practical rather than moral or ideological considerations. It's like playing chess where you make moves based on strategic advantage rather than personal feelings.
Prussian Militarism: This refers to the influence of military leaders on the policy-making process of the Prussian government. Imagine if your school's football team captain had significant say in deciding school policies - that's similar to Prussian militarism.
German Unification: The process by which various independent German-speaking states were unified into one country under the leadership of Prussia. It's akin to merging different clubs in school under one banner for greater impact and unity.