Windowing

Hello I am taking CCNA1 in high school and I am having a hard time describing what Windowing is could someone please brighten up this subject for me?

Windowing determines how much data a machine can send at one time before a host sends information back.Whatever you set as the window size it must be acknowledged before it can send anything else.

eg. say the window limit is 8 bytes then each byte must be acknowledged by the destination host before it can send anymore.