they told me to track it online?
A tracking number is usually the number they will send you in an e-mail. It links you to the company they shipped your product with. It could be UPS, Canada Post etc. and then you go to the shipping webpage and type in the number and it will tell you where it is, that way you can track how long it takes to get to you and if it's going to be there soon. As well it's convenient if something goes missing because they can look up the number (it's easier to find)
Hope this helps!
Where I live, the postal companies give package tracking numbers. So if I buy something on amazon.de and they mail it by Deutsche Post, then they get a tracking number.
I can take that number an go to Deutsche Post web site and enter it there. Then the site will tell me "You Package is in the packet distribution Center in X-city." or "Your packet is in a car that goes from x-town to y-town."