Smart Blocks allow you to set and edit content once and have it show anywhere where you add the smart block [TAG] to your content.
It also allows you to update content in one place and have the content update anywhere the [TAG] is used.
It is useful for adding facebook widget embed code or other code-based widgets which cannot easily be added using the Drag-drop and Contentbox editors.
It is also handy for repeatable content such as Size Guides or Staff Bio information e.g. for the writer of a set of blog posts.
Smart blocks can be found under the Design tab -> Wording / Language heading -> Smart Blocks.
You will be shown a screen where you add new smart blocks or manage your existing ones.
To use a block on your website put [your tag name here] this will enable you to have consistent information around your site.
This can be added to any content area when editing content.
For example if you put your conditions in a smart block then added the tags in relevant places, you would only need to edit the smart block content once for it to update everywhere it is used.