Happy to help, and I know it can be really overwhelming getting your feet wet in Infusionsoft!
What I’m talking about is actually all “Campaigns”, and it’s all in the visual “Campaign Builder” with the graph paper background and the drag-and-drop elements you’re already working with! A “sequence” is just the rectangular box that you can drag onto the page, and the Email and Timer go inside. So if you’ve set up an Email element in campaign builder, you did that inside of a sequence!
The main issue is how many email you have inside of one sequence. If you’ve got a lot, then a contact that goes into the sequence will get all of the emails one by one according to the timers, and if you pull them out and put them back in again they’ll get all of the emails again that they’d already gotten in the sequence so far.
So if you need to pull someone out and put them back later but not have them get the same thing twice, you’ll need to make sure that you only have one email inside each sequence. It’s just a design decision and it probably means you’ll have many sequences inside your campaign instead of just a few sequences.
Hopefully that helps clarify a little bit!