When creating a Post or even managing a page in Locable you'll notice a small option in the upper right hand corner to Toggle Advanced Settings.
When clicked this exposes a couple options for you to explicitly define the description of your content (or page) as well as the "official image," these are then used by Google, Facebook and others when present your content in search results or Newsfeed's, respectively.
1. Meta Description - This is simply the description of content that will appear in search results or on someone's Newsfeed etc.
It's recommended to keep this to around 160 characters, it should be punchy and compelling but don't give away everything in the description. This should be the teaser, think about movie trailers, enough to get people interested but not so much that they don't have to actually read the content.
2. Custom OG:Image - This is the image that will appear in the newsfeed or, occasionally, in the search result.
What if I don't use the Advanced Settings?
If left blank both Google and Facebook will guess at your content. Generally this means they'll take the first 160ish characters of your post (body content) and an image.
What this means is that it's entirely possible Facebook will show the wrong image or one that doesn't make the post very clickable while the description will lack that added hook to get people to click. The net result is fewer clicks, fewer visits and poorer SEO & Social media performance (both Facebook and Google track click-thru-rates in determining content quality and relevance).
It's worth the extra 30 seconds.