Okay kiddo, have you ever played with words before? Mesostic is a type of word game where you pick a word, and then you create a new word by crossing it with other words. Here's how it works:
Let's say you pick the word "LEMON". Now, take another word, let's say "OCEAN", and write it vertically like this:
O
C
E
A
N
Now, try to make a new word by having the letters of "LEMON" cross with the letters of "OCEAN" wherever they match. For example, you could make the word "CLoNE" because the "O" in "OCEAN" matches with the "O" in "LEMON".
That's a mesostic! You can keep doing this with different words and see what new words you can create. It's a fun way to play with language and come up with some unique combinations.