Macros are for repetitive tasks that require the same series of actions over and over again. TextMate’s macro engine is similar to something like the Script Editor and the latest Automator’s “Record” function. Or could be compared to recording a video and then watching be played over and over again. Where in this case you are recording actions or modifications and repeating them however many times you implement the Tab Trigger, or Key Command.
One example is a macro that I created that mimics Vim’s “O” command (insert text above current line).

Now every time I press ⌘⌅ (Command+Enter), it adds in a line above the current one, and then moves to it begin typing.
I created this macro by starting the recording (Bundles –> Macros –> Start Recording or ⌥⌘M). Then ⇧, ⌘⇨, ⏎ (That’s: Up, Command+Right, Enter). Stop recording (⌥⌘M), to test out your Macro you can use it with ⇧⌘M, if you want to keep it; press ^⌘M which will open the Bundle Editor and there you can choose whether you want it to be implement with either Key Command or Tab Trigger, and then the Scope of it.
Vim’s macros can be made by doing in normal mode: q(insert letter here), do the macro and the finish the macro by using “q” again in normal mode and to use the macro use @(whatever letter you assigned the macro).
