This is another way we can talk about numbers. If you've watched the above clip, you'll understand that "single" means 1, "double" means 2, and "triple" means 3. There are also words for four and above, but are less commonly used (scroll down to the bottom to see all the numbers till 10!)
Some other examples of them being used in real-life:
(1) I only have a single key (meaning: I only have one key)
(2) Could you please double bag my groceries? (meaning: Could you please bag my groceries with two bags?
(3) Listen to my advice if you want to triple your reading speed! (meaning: Listen to my advice if you want to increase your reading speed by three times!)
You might have also seen these being used when talking about accommodations, for example, when booking hotel rooms. There may be single rooms, double rooms, triple rooms, or even quadruple rooms for families. Of course, it's probable that the higher the number of people you want to fit in the hotel room, the higher the cost will be.