Ok kiddo, so have you ever heard of the word "lemming"? It's a small rodent that lives in the Arctic. Well, "lemmatisation" is kind of like turning all the different forms of the word "lemming" into the same basic word.
So let's say we have a sentence that goes like this: "I saw a lemming running through the snow. Then another lemming appeared and started nibbling on some grass."
Now, even though we used the word "lemming" twice, each time it was in a different form. The first time it was "running" and the second time it was "nibbling". But since they both mean the same thing (a lemming doing something), we want to turn them both into the same basic form of the word, so it's easier to work with.
That's where lemmatisation comes in. It's a process where we take any word and find its basic form in the dictionary (like "run" instead of "running" or "nibble" instead of "nibbling"). This way, we can lump all the different forms of the same word together and treat them as a single unit. It's helpful when we're trying to do things like analyzing text, so we don't have to keep track of every single variation of every single word.
Does that make sense, kiddo?