The WooCommerce Recommendation Engine is a plugin for WooCommerce that uses artificial intelligence and machine learning algorithms to analyze customer behavior and recommend products that are likely to be of interest to them.

This can help online store owners increase sales, improve the customer experience, and provide automatic cross and up-sells.

The extension provides three types of product recommendations:

1. Related Products By View: This module shows products that other customers have viewed alongside the product that the customer is currently viewing. This data is recorded in the recommendation engine database and is processed to suggest products that are often viewed together. This helps customers to find related products that they may not have otherwise found, and can be an excellent way to provide automatic related products.
2. Related Products by Purchase History: This module shows products that are often purchased by the same users over time. The products do not need to be purchased at the same time. This type of recommendation is an excellent way to get users to purchase more products at the same time by showing them things that other users have come back to the site to purchase later.
3. Products Purchased Together: This module shows products that are frequently purchased at the same time and in the same order. This type of recommendation is an excellent way to build and show a database of products that are often needed together to complete an order. Often times accessories or other types of add-ons will be purchased at the same time by a user, and this engine will show those bundles to end users. This can help shoppers to discover products that they might not have been considering or had thought they would need.

In addition to these recommendation types, the WooCommerce Recommendation Engine also includes two widgets:

1. WooCommerce Recommended Products: This widget allows store owners to show the Related Products By View and Related Products by Purchase History recommendations.
2. WooCommerce Purchased Products: This widget allows store owners to show the Products Purchased Together recommendations.

Overall, the WooCommerce Recommendation Engine is a powerful tool for store owners who want to increase sales and improve the customer experience by offering automatic product recommendations based on customer behavior and purchase history.