Okay kiddo, have you ever seen how in your computer or phone sometimes some letters or characters look a bit different from the others? That's because they are from a different language, a different way of writing.
Now, some computers need to be able to read and write in different ways, and that's why they have something called a character set. Think of it as a list of letters and characters that the computer knows how to use.
The Lotus Multi-Byte Character Set is a specific list of letters and characters that was used by a computer program called Lotus. This list includes not only the usual letters and numbers that we use, but also characters from different languages like Chinese or Japanese.
These languages need more than just one byte (or little block of information) to represent their characters, because they have a lot more characters than what we use in English. So, Lotus Multi-Byte Character Set was designed to be able to handle all of these different characters without getting confused.
Basically, the Lotus program needed to be able to understand and display all of these different characters correctly, without mixing them up or showing them in the wrong way. And that's what the Lotus Multi-Byte Character Set helped it do.
Hope that helps, kiddo!