"People You May Know" is the feature of facebook which helps you to connect more people around the world. Sometimes they are known to you and sometimes they may be unknown people.
Check for any new request by going to the option as shown in below image.
AT the next page you can find people you may know. For example some people are shown in the below image. If i want to connect to any one then i can click on "Add Friend" button. Hence in this way i can use this option to connect with more people.