Dumb embarassing question:

what does year over year and month over month mean?

I think the term comes from the way it’s calculated…

yoy sales growth = (year 1 sales / year 0 sales ) - 1

y/y is compared to same period in the previous year. Month over month or quarter over quarter is sequential (compared to previous month or quarter).

Right. Year over year helps control a bit for seasonality effects, and automatically annualizes the figure.

Something that should be covered in CFA level 1.

Everyone else said this so I will just add some context:

YOY or Y/Y is relevant particularly for growth stocks because people want to see how the growth is tracking relative to the same seasonal period last year.

For non-seasonal or hyper growth stocks the Street will sometimes (but rarely) focus more on Q/Q numbers to see how the growth is occurring regardless of seasonality (if any). Some high flying stocks like SaaS stocks are modeled, valued, and tracked on Q/Q numbers.