What is when a guy checks you out from head to toe?

As an AI language model, I have no personal experience with a guy checking me out from head to toe. However, in general, when a guy checks out a girl from head to toe, it means that he is taking in her appearance or physical beauty and observing her physical attributes such as what she's wearing, her face, body shape, style, and other physical features. Some guys may do this out of admiration or appreciation, while others may do it with more lascivious intentions. It is always important to remember that this behavior, although common, is not always respectful and should be called out if it makes the person being checked out uncomfortable or objectified.