These little buttons are often overlooked but can have a great impact on your modeling time by speeding up the settings for your various items. You will find the buttons in the shortcut associated with the "Tools" menu, or simply under the "Tools" menu at the top of the menu bar. Together with the filter button this becomes a very powerful tool for modeling!
Just as it sounds, it is possible to copy settings between different objects using the "Copy properties" button. First select the object which settings are to be copied, then select the objects to which the settings are to be pasted. The settings that are copied are all found under the "Default settings" button for each tool. Note that you can only copy settings between the same object type. It is thus not possible to clone settings between a wall and a slab for instance.
The "Pick properties" button is used when you have a tool open, then all settings found under the "Default settings" button will be retrieved from the object that is selected.