设置100%到一个div的宽度和高度的逻辑。

This might be a silly question. However, I couldn't find the exact reason for this question. Whenever I set 100% to width and height of a div it doesn't take this behaviour but when I set the width and height of the Html and body elements to 100% then the div with 100% size works perfectly. What is the reason behind it? Thanks in advance :)This might be a silly question. However, I coul