Okay kiddo, imagine you have a bunch of friends who all speak the same language, but they live in different parts of the country. They might use different words, pronunciations, and even grammar rules sometimes. This is kind of like what happens with Serbo-Croatian, which is a language spoken in different countries like Serbia, Croatia, Bosnia, and Montenegro.
Even though they all use the same alphabet and understand each other, the way they speak can be a bit different. There are some different words for things, like saying "hvala" in Croatia instead of "hvala ti" in Serbia to say "thank you". There are also different ways of saying the same word, like the letter "c" being pronounced "ts" in some places and "ch" in others.
Another thing that can be different is the grammar rules. For example, in Croatia you might say "vidio sam" to mean "I saw", while in Serbia you would say "videh". They both mean the same thing, but they use different forms of the verb.
So, overall, Serbo-Croatian has different standard varieties, depending on where you are in the country. They may sound a bit different or use different words, but they can all understand each other!