Machine Learning....

Suppose your friend invites you to his party where you meet totally strangers.

Since you have no idea about them you will classify them on the basis of gender, age group, dressing, or whatever way you would like using no prior KNOWLEDGE.

This means You use UNSUPERVISED LEARNING.

Now you go another party and you have some prior data of information about all,

Then you will recognize them on the basis of your information.

That technique called SUPERVISE LEARNING.