Okay kiddo, have you ever tried to say "uh-oh"? Did you notice that little sound you made in between the two words, almost like a tiny cough? That's called a glottal stop.
The glottal stop is actually a speech sound that is made by briefly stopping the flow of air in your vocal cords while you're speaking. It's like a tiny pause in the middle of a word or syllable.
Now, when we write down words we don't always include every sound. For example, in English we don't always write down the sound for the glottal stop. But some languages do have a letter that represents this sound, like the letter "ʔ" in some languages spoken in the Pacific Islands.
Overall, a glottal stop is just a small pause in your speech that can be represented by a letter in some languages. It's like a tiny cough sound you make while talking. Cool, huh?