Ipad

Have both of your iPads been updated to iPadOS?

The aA icon - at the left-edge of the address field, was newly introduced within iPadOS/iOS13. Tapping the aA icon summons a new menu, where you can now select various browser options/settings.

Prior versions of iOS would, on certain web-pages, instead show a Reader View icon in this position - which, if tapped, would switch the browser into its reader-mode.

I hope this helpful in describing what you are seeing and why.

I don't think it's really "there". I think it is a placeholder put there to remind you where to type your input on that screen. Click in the box and start typing. I bet that the aA disappears without you having to erase it.