Assertion-Reasoning-Evidence. An argument. The most basic part of the debate. The assertion, the tagline of an argument. It is a sound bite that should, in a quick sentence, summarize an entire paragraph worth or reasoning and evidence and tie things all together under one idea. Reasoning is how you got to the assertion. Your train of thought. The logic behind the assertion that links it to the evidence. Evidence is what makes the argument true. It is undebatable, 100% pure scientific facts backed by a reputable source. The A-R-E format is the nucleus of the debate.
An assertion is defined as a point of information that is debatable. Facts are not assertions. Neither can evidence be or accepted truisms. An assertion is a statement that can be debated in a debate round. It should also be short, sweet, and to the point. Assertions are also synonymous with the overall argument. To clarify: most judges usually just right down the assertion and listen for reasoning and evidence. If the reasoning and evidence make sense, then the assertion is checked. If it doesn't, then the judge may discredit the assertion.
*Assertions are synonymous with "argument" or "point" in debate. 'That assertion doesn't make sense' just means that the argument said by the other team didn't make clear sense.
Reasoning is what links the argument to a known fact, or the evidence. Reasoning shows the judge how exactly you got from fact A to assertion Z. It is like a road map that explains your logic and why you assumed assertion A to be true. Reasoning is often the weakest link of the three parts of the A-R-E argument format, and is what is usually refuted by opponents when trying to contest your points. Reasoning should be the longest part of an argument, usually three sentences to a paragraph long. It is often what judges will use as the basis for their speaker scores. "Oh, you had crappy reasoning" or, if you use this website, "Oh, I almost fainted that reasoning was so GOOD!!!!"
Evidence is basically a fact or facts that support the assertion in which they serve under. Evidence is crucial. No evidence=a mute point. If an argument is called out for evidence and there is none, then the argument is immediately nullified. Evidence is just irrefutable, plain, scientific-based facts that make an argument either true or false. It is crucial to have good evidence. Even just one piece of mediocre evidence is good enough because, since it's evidence, it is irrefutable! Evidence is key to success.
The A-R-E format stands for Assertion, Reasoning, Evidence, as you already know. It has to be in that order when you say it. It is essential to distinguish to the judge what parts of your arguments are the A, the R, and the E. Once you've mastered the format, nothing will stand in your way of presenting your arguments effectively, effeciently, and excellently.