When a search query is submitted to the index, each document that is returned has a search score which is an indicator of its relevance in the current search query and context. The higher the score, the more relevant the item and therefore, the higher it is ranked on a scale of high to low.
In Azure Search, you can tweak the calculation of a search score through an index modification called a scoring profile. A common usage of scoring profiles is Geo-search, which allows you to automatically boost items which are closer to the location of the user. You can also simply boost by pushing newer documents to the top of your search results, or in some cases boost some older documents. It all depends on what your business needs are.
You can configure as many scoring profiles as you would like in your search index, but you can only specify one profile at a time when running a query.
Scoring Profiles vs. Managed Property Weighting and XRANK
For the SharePoint Devs out there getting into Azure Search, Scoring Profiles is a lot like Managed Property Weighting combined with XRANK in SharePoint. However, I find that Azure Search gives you control that allows you too really customize your boosting in ways that SharePoint cannot. Most of your boosting control comes in how you define your scoring profiles in your index, which allows you to really clean up your query on the front end without having to use XRANK. For example, to achieve a simple Geo-search, you would only need to provide the scoring profile and the current location as parameters in your search query.
As a further bonus, you can configure as many different scoring profiles as you would like, giving you full control of how your query gets processed. While in SharePoint, you can only configure a single set of relevancy rules without using XRANK, in Azure Search you can configure as many as you would like and specify which one you would like to use at the time. This way you can specify different weights for different fields (managed properties) when your business needs change without having to completely clobber the back-end index.
Having the ability to change scoring profiles as your user navigates through different portions of your website gives you a great flexibility. You can control a lot of what occurs in your search queries by modifying the scoring profiles in the index, rather than piece together complex queries. It is simply a cleaner way of making things happen.
Stay tuned for some physical examples! For a detailed msdn article, please go here.