Connected postings are two or more postings that share a common set of content. If one of the postings is edited, the changed content is reflected in all the connected postings.
We could add a bit more of a description as to why, something like this: It may be a requirement of site design that the same content be reused in different areas of the site. If the content is changed in one area of the site, then the change is reflected everywhere this content is displayed. This reuse of content is the reason behind connected postings that is, a single set of content is included in a number of different postings throughout the site. To allow even greater flexibility, different, connected templates may be used to repost the same content. Having different templates to repost the same content means that the content can have different formatting, the arrangement of placeholders may be different, only a subset of placeholders may be displayed, and so on. If you want to use different templates for connected postings, the templates themselves must be defined as connected. One of the biggest advantages of connected postings is that since each posting is stored in a different channel, you can effectively limit who can see what posting.
Essentially, think of connected postings as separate entities in CMS that both display the same content. Unlike the copy function in the edit console, which duplicates the content, connected postings share one content source; if you change the content in one posting, the resulting change is automatically reflected in the other connected posting. Now, having two postings sharing content is really only half of the story. In order to create connected postings, you must also create a set of connected templates.
NOTE: It's possible to create a connected posting with only a single template. In some cases this is desirable, because you can deposit the connected postings in different channels for security reasons. However, in most cases, connected postings are likely to use different templates.
Connected templates are actually the basis for connected postings. Connected templates are two TGIs that share the same definitions and custom properties. Because they share placeholder definitions, it's possible to ensure that content can be automatically repurposed across postings. In fact, it's not possible to create a connected posting with two templates that aren't connected.
Once the TGIs are connected, they are each pointed to a different template file. What this allows you to do is to share content across two postings with potentially different placeholder controls and/or visual design. Now, there are some rules you need to understand when working with connected postings; the short list follows.
Now that you have the basics of connected postings, let's examine how you go about creating connected postings in CMS.