The build() method generates all the composite actions. The following is the syntax for this function:

action.build();

The following code snippet explains to you how you can generate actions using the build() method:

Actions action = new Actions(driver);
action.click(driver.findElement(By.locatorType("path")));
action.build();

The click() method performs a mouse click on the current mouse pointer location. The following is the syntax for this function:

action.click();
action.click(driver.findElement(By.locatorType("path")));

Unlike clicking on the mouse's current location, this function allows you to click on an element by locating it (using the Actions class). Please check the following snippet for both cases:

driver.get("http://www.google.com"...