I see a lot of posts in Ableton Facebook groups that make it clear that the poster doesn't understand the signal flow in Live. The signal flow is the path that the audio signal takes from the input to the output. Why is this important? Well, in between you have Ableton Live which allows for pretty complex routings and you need to know where the audio is affected in which ways to make the right mixing decisions. The signal flow within an Live track is still fairly simple, as I've already explained as part of my gain staging tutorial, for which this knowledge is also vital. It can become complicated quite quickly if you make use of the sends, groups and the flexible routing options. Since a picture is worth a thousand words, I've created a graphic that you can pull up when needed or use as a background wallpaper on your computer.
A quick walkthrough:
The input comes either from an audio input, which can be an external source or another track in Live, or a clip. It then moves from left to right through the device chain on the track, then through the mixer section with panning and volume settings, then out through the designated output. Then it forks off depending on the output setting to another track or group track in Live, the Master, an external output or the Sends. Except for the case when it's sent to an external output, it again runs through the device chain on that track, through its mixer section and then to the set output. What isn't shown in the diagram is when an Audio From setting is used in a track. Then it takes the audio from the output of the set track as an input, while the rest remains the same.
If you're using the Sends, the signal path depends on the Pre/Post Toggle setting for each that you can find in the Session View in the Master track parallel to the Send dials. Pre and post is short for pre fader and post fader. This means if Pre is on, that the audio will bypass the mixer section of the track and be sent straight to the corresponding Return Track. The default setting for it is Post, which means the audio is tapped after the mixer section of the track and only then sent to the Return Track.
I hope you will find this graphic helpful. Let me know if you have any comments.