Ongoing capture is the constant process of capturing what's important to deal with later. It's maximizing the value of any given thought. It's ignoring what's not important. Ongoing capture enables supplies the content for Periodic Reviews to sort through and make use of at later, dedicated (via Time Blocking) time.
I see 3 categories of ongoing capture. As you go about your day, you run into the need to do something later (Capturing Tasks), you may learn something or think of something you want to remember (notes), and you do things that you want to keep record of - for reference or as a measure toward KPIs or OKRs (logs)
Mapping these processes to their tools and systems is a part of the Master List.