You only have 2 apples...
And you're supposed to give your friend 5 apples... 
You go ahead and give her the 2 apples you have...

And, then, you'll still owe her 3 more apples!

For those of you out there who are old enough to have a checking account (or a pretend one for learning), it's like having only $2.00 in your account and you write a check for $5.00...  So, you are overdrawn (in the hole) by $3.00!

One of the places that I'll bet you've already heard of negative numbers is with temperatures.  I'm sure you've head someone say, "It's 20 below!"  That means it's -20 degrees - which is very cold! Don't worry about needing to know how to add and subtract with negative numbers yet.  We've got some other things to talk about first!