The term Knowledge Graph refers to search results prepared and compiled on certain topics and entities, such as people or areas, in Google and Facebook search. The two companies differ, however, in the complexity and nature of their knowledge graph. The knowledge graph can be interpreted as another step on the way to a semantic search.
Google knowledge graph
With the Knowledge Graph, Google introduced a system in May 2012 that cumulatively aggregates data about people, places, and events and graphically summarizes it in a separate area of SERPs. With the Hummingbird update, Google has also expanded the functionality of the Knowledge Graph, which, since then, can now also be used for comparisons.
Google uses a separate algorithm for the presentation of results, which scans the search engine index for structured data and then issues it with specific search requests on "important people, places or things"  According to Google. Wikipedia information is usually used for places or celebrities.
The Knowledge Graph can be used on any device, in other words, on PCs and mobile devices such as tablets or smartphones. The following are the characteristics of the Knowledge Graph:
Google can provide more information about series with a carousel.
If you click on an image within the carousel, a new Google search page will appear for that term.
Separate results box
Google accumulates information and structured data about the search term from different sources such as Wikipedia and orders them in a new and understandable way, for example, in the upper right part of the page. This results box is not directly comparable to Google's OneBox, since Google only uses its own data from Google Maps and Google My Business.
Comparisons in the results box
With the introduction of the Hummingbird update, Google has expanded the functionality of the Knowledge Graph so that it is now viable compare different entities such as buildings, food, or planets.
Google Reply Box
The Google Knowledge Graph has found its own expression in the Answer Chart. This box was introduced by Google in 2015. It provides users practical answers to questions about definitions or phenomena.
The Google Knowledge Graph and the consequences for SEO and SEA
Following the introduction of the Knowledge Graph, Google has strengthened its position as an "information provider." In this way, if you are doing a superficial search and looking for a short answer to a question about a poet or a thinker, then you should not leave the search in the Google search engine. The consequence for informational websites could therefore be a great loss of traffic. If these sites are also used for affiliate marketing or display marketing, the lowest ad rates can be expected.
There is no longer viable optimization potential for places, artists, or some facts for individual keywords or two-word queries as a result of the knowledge graph, but rather in the long tail area. In this way, SEOs more than ever have to anticipate what users are looking for and how they are looking for it.
With the Google Answer Box, webmasters at this time have the opportunity to be ranked first in the SERPs, even though the page is not in the top 5 in organic results. Therefore, the Knowledge Graph allows you to generate reach and fame for your own website. However, a screen in the answer box is not a guarantee. Google's algorithm uses its own criteria to establish which text items or revision marks it uses to answer questions.
How the Knowledge Graph works with Facebook
The social network Facebook has its own knowledge graph since 2013, which is called Entity Graph or Facebook Graph Search on Facebook. For this, Facebook uses the community pages introduced in 2010. Like Google, Facebook uses external and proprietary sources for data collection. The data for the entity chart is sourced primarily from Wikipedia.
The Facebook knowledge graph is displayed when using Facebook internal search and logged in. Additional results from the network are added to the searched item, location, or person on the summary page.
If you want, for example, "Leonardo da Vinci", you will have additional information about the nationality or profession of the person sought. Clicking on one of the results will take you to another related group or community page.
The prerequisites for displaying an Entity Chart are that the appropriate community page for the request has not been claimed. Similarly, official fan pages or company pages are not linked to the Facebook knowledge graph.
Consequences of the Facebook Entities Chart
Like the Google Knowledge Graph, the Facebook Entity Graph can lead more users to use Facebook just to get information. Once again, there is a risk that pure information sites on the Internet will lose traffic if more than one billion Facebook users only access the data offered by the social network.