What does myFunction(this) pass into the this parameter?

In my HTML I have <span><input type="text" class="tester" onfocusout="tester(this)" /></span>
When I console.log the passed in value for ‘this’ I get: enter image description here

Now from within my Javascript I want to grab an element in just the way the ‘this’ paramater did. .innerHTML logs a string and .getElementsByClassName an array. If I define the index of that array it will return input.tester.
How can I get the ‘live’ HTML element like in the picture? Thank you.