Orthography is a fancy word that means the way we write words on paper or computer screens. You know how you learn in school to write letters and words? This is what orthography is all about, making sure we write everything correctly so that others can understand what we're saying.
For example, you might see a word written in two different ways "color" and "colour". Both are correct, but one is used in America, and the other in Europe. Orthography helps us understand the rules of spelling and grammar, so we can write and read everything correctly.
Orthography might sound complicated, but as we learn more, it becomes easier. So keep learning and writing, and you'll be a spelling expert in no time!