I think you mean PinYin. For example you can represent a word like 我们 (means `we`) as wo3men2, but 我门 (means `my door`) is also pronounced as wo3men2. That will be tricky if you write something like wo3men2huai4le, it can be either 我们坏了 (means we are badass), or 我门坏了 (meaning my door is broken). And that's why early pinyin input method is a nightmare to use, because it often suggest unrelated candidate. Now with smarter software, the input method is more likely to suggest the later option instead of saying you're badass.