This is configurable in the side panel settings. Depending on the field type, it will present itself differently.

Linked Records - Find the Link/Unlink setting.
Formulas - You can't edit because the value is determined by the formula, not inputted by a user
Pretty much any others looks like this and you can toggle between them.

There is Documentation here:
Configuring Elements in Interfaces | Airtable Support

Look for "Making elements editable for collaborators"

Just to add, here's a fun little thing I built.

I wanted my interface to have static information, but I also wanted a button to enable editing. It's sort of like viewing your contacts on your phone. I made a workaround for it.

I first duplicated my static interface page and hid the copy from the navigation. With the copy, I toggled the fields I wanted to be editable. Next, I created two formulas to find the URL for both the "Static" and "Editable" record details page. I then made a button on each interface to redirect you to either the static or editable sides.

The URL formulas look something like this:

"https://airtable.com/app...../...../" &  RECORD_ID() & "?....."

From the user side, it all looks like I've created a toggle when it's actually redirecting you to a secret editable page.