Not sure why I'm getting "[@[Header]]" when trying to reference a table for a formula

Hello,

When I was trying to use VLOOKUP in excel, I needed to reference cells within a table for the lookup value; however, when I click on those cells, instead of getting "A2" or something similar, I got "[@[Header]]", where "Header" is an arbitrary name for the header of the respective columns that I attempted to reference cells from.

ex: When clicking A2 as a reference for the lookup value, instead of "=VLOOKUP(A2, ..." it would look like this: "=VLOOKUP([@[Header]], ..."

This isn't a huge issue, I already bypassed the problem. I was just curious why that is and I wanted to learn a little. Thanks for any info! :)