Create a new type of text widget?

I’m reading tutorials on how to create a custom plugin/widget but I’m missing what’s probably the easiest part of it.

Basically, I want to create a new widget with a custom background via CSS and the ability to put text over it. I see how to get the widget to exist as a plugin but I the tutorials I’m reading have much more complex functions in there, such as random post queries.

What is the function for simple text input on widget?

Thanks!