It depends on your routing setup. There are two basic scenarios:
Aux Sends ➤ Aux Channel Strip
With this setup, you use the Aux Send on individual Channel Strips to send their signal to the Aux Channel Strip that usually has FX like a Reverb or a Delay. By sending portion of the individual CHannel Strips to that Aux CHannel Strip, you effectively adding Reverb or Delay to that signal
Output ➤ Aux Channel Strip
WIth this setup, you send the Output of individual Channel Strips to the Aux Channel Strip. This is called an Aux Group or Audio Group and is usually used for submixing. For example, route all the Drum Tracks or all the Vocal Tracks to an Aux Channel Strip and control the summed signal on the Aux Channel Strip.
The Summing Stack is using this type of routing where the Main Track is the Aux Channel Strip and all the included Subtracks are the Channel Strips that route their output signal to that Main Track via a Bus. A Summing Stack just has more advantages when it comes to organizing and grouping your Tracks and I would highly recommend using that feature.
Here is a short excerpt from my book explaining what happens when you create a SUmming Stack

Hope that helps
EdgarRothermich - LogicProGEM.com
(Author of the "Graphically Enhanced Manuals")
http://DingDingMusic.com/Manuals/
'I may receive some form of compensation, financial or otherwise, from my recommendation or link.'