Contextual link is a clickable word or phrase in the content that directs to another content, material, post, page within the website. Contextual, content, internal links is a strong SEO technique to grow sales, improve page rank, credibility and popularity of your website for search engines. 

One of key aspects of internal linking is that they increase involvement of users on the website. When the user sees the informative link-anchor which leads to relevant content, they possibly will follow such link and will spend on your website longer time, viewing more of your content, goods and services you offer and want to sell eagerly.
Thus, internal contextual links is necessary and benefitial for both sides , for the sellers and for shoppers. For you - webmaster, seller, whoever- Content Links will help to improve search optimization of your online store or whatever, improve its position in Google and other search engines, build solid trust of search engines, promore specific products and double your chances to sell more; for customers - it will help them to find information, useful and interesting to them, since contextual internal links creates a good website links network that results in a nice navigation around the website. 
How to create contextual internal links automatically? 
At wordpress there are several worthy SEO plugin for interlinking that provide qualitative and legal internal link-building. 
1. SEO POST CONTENT LINKS by WPAdm is a wordpress plugin for automated creation of content / contextual links within one website. It has some advantages among other seo plugins. 
 

• Content links has 2 versions - free and paid that pocesses wider functionality and useful features.
  
  Free version allows to build internal links automatically on a random basis.
  
  
• It allows to specify number of links that should be created on website.
• Keywords for the future internal link-anchors can be typed manually by the user, or generated automatically by the Content Links plugin.
• Internal links can be added to the H-tags
• Internal links can be created within one category and within all categories 
• Content links allows to create personal list of blackwords that should not take part in interlinking process
  
  
• Content Links PRO version has wider functionality that can be effective and important for online stores and other site to sell goods and services. 
  
  
• Content links pro allows to links particular posts internally
• it allows to builds internal links among specific pages and categories
• it allows to link all posts/pages/categories to one particular one with the aim to improve its page rank. This way you can faster sell desired product or service, because the links from all posts will lead to this product, increasing its popularity and page weight, making it possible to return this  very page in search results, as well as your website users will often find this product on your site. 
• content links pro allows to change links color and size, giving it "follow" or "no follow" status and much more.
  In PRO version you can select 1 particular post, for example the one that contains some general info, in my case it is a list of Europeans cities to visit, and you can build links from this main post to separate posts that contain more delailed info, thus navigating users to read more material on your site and make an order. 
  Below you can see my settings for internal links:

Here you can see some examples of created links on my posts. The Seo Internal Links plugin made links taking into account my settings as for link design and keywords that became link-anchors.