The 'Macro Recorder' monitors your mouse clicks and keystrokes to convert them into actions.
If you want to populate a textfield element, you would normally first click on it and then type your text.
By default, this is converted to a 'Click Element in Window' and 'Send Keys' actions.
However, if you want to automatically convert it to a 'Populate Text Field in Window' action, you should right click first on the textfield element, which will "lock" the element with the UI spy inspecting orange box and then send your keystrokes.
The aforementioned method will create a 'Populate Text Field in Window' action instead of Send Keys'.