Yea, off-season/non-peak season is when most people refrain from traveling to a particular location, either due to less favourable weather, lack of events or general holiday patterns. It’s also called bumper seasons in the airline industry.
Off-season has some general patterns but varies from location to location.
Examples:
Peak season to go to Dubai is in December because the weather is far more tolerable. Off season would be June-August. Weather gets to like 110 F.
Europe; In general, most of summer is peak season. The weather is the best and a lot of tourists flock in. Also, a lot of Europeans head out. Off peak is like Feb-early May.
Rio and NOLA’s peak season is usually around Carnival/Mardi Gras, and then it tables off from there.
I like traveling in off season when I want to avoid crowds, tourists and when I want to get a more “local” experience. You also get better prices for the most part.