well actually there are javascript events fired when you click, but they may not be the ones the particular element is looking for. And sometimes an element has to first be put into a state where you can click on it via something like a mouseover.
so the trick is generally figure out what events need to be fired (see Zeljko's answer) and then use the .fireevent method to fire those events against the elements that need to see them, in the order that is required.
a lot of times you pretty much have to reverse engineer what the developers are doing by looking to see what elements in the html are looking for what events.
In this specific case, if your intent is to click the BLUE learn more button that seems to be on top of some kind of screen shot, then examining the HTML or The DOM shows that it has a convenient ID value which could be used. You can also see it is 'wired' to respond to the onclick event, and more importantly it is opening a new modal window (in this case a div that looks like a popup) onclick="new Modal('learn_more_content', {top: 110, modalClass: 'borderless'}).show()
. so the following code ought to work to launch the modal
browser.button(:id, "learn_more_btn").click
Then to click the green 'get started' button (of which there are several so we need a way to indicate which one)
browser.p(:class, "cta").button(:class, "green button has_arrow").click