In your daw, you will have one, or several tracks. Each track will play a single stream of audio, either in mono, or in stereo. Once this signal is played, it then goes through the channel strip. The channel strip is the area where you can insert effects, and sends. This lesson is focusing on the effects, but for more info on sends and aux busses, check out lesson 4.1, using aux busses.
Every daw comes with a wide range plugins. They can be instantiated within any track to sculpt the sound. I personally put eq and compression on nearly every track, but I would suggest going through your plugins and experimenting with them. They are your tools of the trade, and the more familiar you are with them, the better your mixing will be.