A button's style determines how the button appears and how it responds to user input. The TBSTYLE_BUTTON style creates a toolbar button that behaves like a standard push button. A button that has the TBSTYLE_CHECK style is similar to a standard push button, except it toggles between the pressed and nonpressed states each time the user clicks it.
You can create groups of toolbar buttons by using the TBSTYLE_GROUP or TBSTYLE_CHECKGROUP style, causing a button to stay pressed until the user chooses another button in the group. The TBSTYLE_SEP style creates a small gap between buttons. A button with this style does not receive user input.