Transcript:

So, someone asked me an interesting question a few days ago, and I had to look up the answer. But here's the question: In our phone, there is a card that allows us to make calls. It's called a SIM card. We always call it SIM card; we never call it S-I-M card. Okay. If you ask somebody who's living in the United States, "Where do you live?" They'll say, "I live in the U-S-A." They never say, "I live in USA." 

So, you see the difference: S-I-M is never spelled out in letters. It's always a word "SIM" and U-S-A is never a word USA, but it's always "U-S-A." So, these short forms are technically different; they're not the same. So, what is the difference? So, what is the difference between N-A-S-A, S-I-M (NASA, SIM) versus U-S-A, T-I-F-R, all the short forms that we say each letter or each alphabet versus when we say it as a word, NASA, SIM, what is the difference? 

Let me know in the comments if you know what the technical words are that differentiate these two types of short forms. Pretty interesting!