What punctuation mark is often used to insert explanatory text into a quatation?

Read this passage from the online article “top 10 reasons why everyone is doing yoga” by kathryn livingston. what type of propaganda is the author using? why are so many people doing yoga these days? there must be more to it than endorphins; there has to be a deeper reason why 20 million plus americans have fallen in love with this venerable practice. here is my top ten list – and if you’re a yogi, i’m sure you can think of more.