Unlike other Facebook plugins which use iframes to embed your feed into your page once it’s loaded, the Custom Facebook Feed uses server-side code to embed your feed content directly into your page. This adds dynamic, search engine crawlable content to your site.
Could You Explain Further?
Is There Any Types of Content That Are Not Crawlable?
Since the image files that create the images in your feed are served from Facebook’s CDN, Google and other search engines will ignore them when indexing. However, the alt text and any link text related to the images will be indexed.