Excel "Macros" are really little bits of code written in the VBA language. While Excel provides many functions, you may want extra functions to automate tasks you do all the time (and it's way easier than coding your own desktop application!) Macros are great for automation, and you don't need to learn VBA to get started.
> The easiest way to start is to record a new macro. On the Developer tab, hit "Record Macro." Name it whatever you'd like and hit OK.
> Do whatever task you'd like to automate, and then click Stop Recording. (An easy test is to add or delete a column, or copy/paste a range of cells.)
> To tell Excel to do the task again, make a button. (There are other ways to call upon macros, but this is one of the most common.) On the Developer tab, hit "Insert"; the button is usually the first icon under Form Controls, and looks like a square.
> Click the spot where you want your button to appear.
> A dialog box will appear; select your macro from the list and hit OK.
> Click your button and Excel should perform whatever task you want!
If your macro is complicated (for example, you want to select all available rows, not just the specific range A1:A100), you may need to edit the macro. Simply choose Macros on the Developer tab, select your macro, and click "Edit." Google is a great resource to help you tweak a macro to work for you!