A class can have child classes so you can create multiple levels of classes. Creating levels of classes gives the user the possibility to manage the traffic that leaves the class. You can specify how the classes behave to each other so you can control the amount of bandwidth a class can get.

The classes at the end of the class chains are called leaf classes. Each leaf class has exactly 1 qdisc attached to it that actual sends the packets. A leaf class is a class with no child classes. Non-leaf classes do not contain a qdisc. Actually non-leaf classes are only used to gorup the leaf classes.

Filters are attached to the root qdisc or a class (parent parameter) to filter the packets that belongs to that qdisc/class. If the packet matches a filter, it's placed in the class spedified with the flowid parameter. Each packet that enters the root qdisc must end in a leaf class so it can be send.
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