This is the plain old button style which contains text as content. However the layout_width property holds another design tweak where the button width would be filled to parent or to be wrapped to content. Even you could fix it to some dp values.
In this style, a button would have an image on the left side and text on the right side. Where @drawable/Icon is the path of the image
In this style only image would be present.
The android:background property is used here instead of android:drawableLeft. Also you could add padding for uniformity in design.
Also we have an ImageButton, which could satisfy our style needs.