On the outside a hub looks very similar to a switch but on the inside they are totally different.
A hub is a central device that you connect other devices to using an Ethernet cable. Any data that is sent from a connected device to the hub is repeated on all the other ports connected to the hub.
In a switch this is handled much differently. When using a switch data is in frames that contain source and destination information. This information allows the switch to reduce the amount of network traffic because there is direct communication between two devices instead of one device sending information to all the devices on the hub.
As you send more information through the hub you increase the chance of collisions. Collisions occur when two devices on the network send data at the same time and the signals actually collide with one another before reaching their destination.
With switches you won't experience collisions since it is a one-to-one communication with each device on the network. This also means that bandwidth is not shared with other ports on a switch.