InfoPath Dev

I have been staring at this screen: https://support.microsoft.com/en-us/office/create-list-relationships-by-using-unique-and-lookup-columns-80a3e0a6-8016-41fb-ad09-8bf16d490632?ui=en-us&rs=en-us&ad=us for a long time, but I cannot quite see where the linkage between the columns is. I don't have Designer or Workflows and for this particular task I am trying not to use Infopath, just do it as a lookup column in Sharepoint > CreateColumn functionality. I have my source list (a simple, 2-column grid of numbers and corresponding text values), and my target list (where I want to create a column that takes a value FROM THE SAME LIST, then looks it up IN THE OTHER LIST, and returns a corresponding column from the OTHER LIST. Is this not possible?

How many lists are involved here? I think we can just lookup to a single other list, and we can return additional column values, but I can't tell what kind of relationship you are trying to create here. Like - if this list item's Category is "Orange", go get a value from another list that also has a Category of "Orange"?

Okay I think I understand what mistake there was in my understanding of Lookup columns. I was thinking that a Lookup column (let's call it Column3 from MainList) could "lookup" the value of ANOTHER column from MainList (let's say Column1), look it up in AnotherList, and return AnotherList AnotherColumn. But what lookup lists are really designed to do is function as a dropdown, and once selected, they will look up their "own" value (the value that was just selected in the very same Lookup column), which is really coming from the other list, and return another column. What I was trying to do unsuccessfully was figure out how to establish a lookup column in my list that could take the value from a different column in the same list, look it up in another list, and return another column from the list. Something easily accomplished in Excel. But I realize now that the lookup column has to be itself the dropdown and also the value being looked up.