This is especially useful when you are looking for a toilet. In case a toilet is labelled with only the Chinese character, this is the character for male, 男.
This is, in fact, a very interesting character because it's actually made of two characters. At the top, you get 田, which means farmland. The character itself looks like a farmland isn't it? At the bottom, you have 力, which means strength. So male is the one who works hard in the field.
From this Chinese character, you actually gain an insight into human history. Nowadays, not all males need to work on a farmland, but this character reminds us the lifestyle of our ancestors. Isn't that cool?
If you are interested in learning Chinese. You should definitely check out this article on how to learn Chinese.