Difference between do_action, add_action and add_filter
It is used to execute the specific function hooked on a add_action in WordPress core or in your theme or plugin. The function is same like echo. It will display the output of add_action.
Function is used to hook a specific action in WordPress. You can add n number of action in WordPress theme and plugin but you cannot use same action cannot be written twice if same add_action it will give you error.
Add filter function is used to override the add_action hook for example if the add action is to display name A and you need to change it to B without removing the add_action then it can be achieved through add_filter(); in the add_filter you need to add the function for converting to B and added into add_filter.