Every brewing device sits on one side of a single line. Filter brewers (V60, Kalita, Chemex, Origami) move water through the bed. Immersion brewers (French press, Clever, cold brew) let water sit with the grounds and then drain. AeroPress is a hybrid that gives you both, depending on how you use it.
What changes between them
In a filter brew, fresh water is always touching the grounds. Extraction is fast and bright. Pour technique matters. The grind has to be finer because the contact time is short.
In an immersion brew, water and grounds reach equilibrium and stop. Extraction is even and forgiving. Pour technique barely matters. The grind has to be coarser because contact time is longer and finer particles would over-extract or clog drainage.
What you should pick first
If you've never owned a real brewer, start with one filter (V60 is the classic, but any conical works) and one immersion (French press or Clever). Two devices, totally different cup profiles. You'll learn faster from the contrast than from owning four pour-overs.
How to know which side a brew is on
Ask one question: can the water leave the grounds whenever it wants? If yes, it's filter. If no — there's a barrier (closed valve, plunger held up, sealed cylinder) holding it in — it's immersion. AeroPress press, Clever closed, cold brew steeping: all immersion until you release.