A Priori Probability

Think: independent variable. That is, it's about the probability of something happening that is the same probability each time.

Like...you ask for a Yelp rating for your baby seal oil scalp massage shop. You get either 1, 2, 3, 4 or 5 stars. That's it. If they don't rate you, then nobody other than you, the client, and the seal would know. So there are only five potential ratings. And that's always the case for each individual event or iteration that you'd ask to be rated post-uh...scalp rubbing.

A Priori: single, same priority.

So what's not a priori? The odds of pulling the jack of spades from a deck after four draws. In the first iteration, you have a 1 in 52 shot; in the second, the denominator changes because that card is burned and gone, so it's a 1 in 51 shot. Each draw has different odds. No matter how much you, um...massage the numbers.