That’s a weird way to describe or classify pi, and I don’t blame you for being confused. What I think they were getting at is that Pi is irrational. It is not the ratio of two integers. It happens to be that ratios of integers (where the denominator isn’t 0), aka rational numbers, have either “terminating” or periodic decimal representations.
To see what I mean about “terminating” decimal representation, try computing ¼. It’s 0.250000000… so it has some various digits first and then just zeroes forever afterwards. We call it terminating because we can represent this as 0.25 and stop.
Periodic decimal representations have a string of digits that repeat. Take for example 3/7, which is
0.428571 428571 428571 428571 428571…
See that text that says “(period 6)”? That means that there is a sequence of 6 digits that repeat over and over again. Period refers to the size of the repeating sequence, and it can be any positive integer. In this case, we have six digits. If you were to start counting up by digit from the 4 just after the decimal place (starting with a 0, then adding one for each digit) you would see that the 0th, 6th, 12th, 18th, (6k+0) and so on digits are all 4, the 1st, 7th, 13th, 19th (6k+1) digits are all 2, and so on.
But pi is not the only number like this. In fact, “most” real numbers are irrational. And by that, I mean that you can create a way to count all the rational numbers one by one, but you cannot count the irrational numbers because there are so many that if you start to count them, you have to skip some. Irrational numbers are so plentiful they kind of overpower the rational numbers. That’s set theory stuff, if you’re interested.
Pi is a ratio though, just not of integers. It’s the ratio of the circumference of a circle to it’s diameter.
(To clarify something here, I’ve talked about pi, normality, and common misconceptions about numbers today (hence “on the topic of pi”) on a few occasions so I assumed Panic saw those and understood my explanations.)