Macros are very powerful and interesting component of salesforce. Macros are like set of computer instructions that executes to automate some task that task can be to assign value in a field, to automatically send an email, to update any field, selecting an email template and more. All instructions that we create using macros get execute on a single click. Macros are mostly use with case feed layout basically to update case and to send quick response to user about any update of case raised by that user.