Chinese writing is attested for well over three thousand years. The earliest large corpus is oracle bone script from the late Shang. Bronze inscriptions continue the story in the Zhou. Seal script is the form Qin standardization made famous.
Later clerical and regular scripts made everyday writing faster. The twentieth century added a political layer: the People's Republic promoted Simplified characters, while Taiwan, Hong Kong and Macau kept Traditional characters as the public standard.
None of that history is required to press Convert. It is useful when you want to know why 马 and 馬 are both "horse," and why a Taiwan file is not a Hong Kong file.
For how characters are built today, read character structure and radicals.