こんにちは (Konnichiwa) JohnB232 and toru e,
Thank you for your question!
There are a couple of different ways we can use this small っ.
Like toru e says, the first way we can use っ is to create a double consonant sound. You can use it in this way when you see two consonants next to each other, like “TT” or “KK." When you see this little っ in the middle of a word like がっこう (gakkō) "school," it creates a double consonant sound, where the sound before the consonant is held for a second. In the case of がっこう (gakkō), the "k" sound is held.
However, when we use っ at the end of a word, it has a slightly different effect!
At the end of a word, っ works similarly to an exclamation mark: to show emotions like surprise or anger.
あっ (A) is exactly the same as あ (a), but by using a little っ at the end, you can add a little more emotion. It also cuts the sound a little shorter.
Remember, when っ is used in the middle of a word, it is showing a double consonant, and when it is used at the end of the word, it is showing emotion: just like an exclamation mark!
I've added the link to our brand new lesson on Japanese pronunciation, just incase you wanted to read a little more about っ.
I hope this helped! Please let me know if you have any more questions!
べんきょう を がんばって ください！ (Benkyō o ganbatte kudasai!)