The introduction and thesis are both key elements in an effective and persuasive college essay. The relationship between them isn't sequential, though. Your thesis statement, which explains your premise or perspective on a topic, is actually part of your introductory paragraph. It can come at any point within your opening paragraph. You could say the thesis is the final statement in the introduction, for instance, if it is the last sentence in the first paragraph.
The primary purpose of your introduction is to outline or establish what you will discuss in the rest of the paper. It might offer a basic overview of a topic, or present the common, competing arguments on a controversial subject. The thesis answers the primary question by the essay's subject or topic or states your position on the topic. For example, in an essay about "The Best Superhero," your introduction could mention some of the most prominent options. Your thesis might be "Superman's combination of powers, charisma, character, likeability and Clark Kent alter-ego sets him apart from all other superheroes."