With the new SharePoint Online being touted as the SharePoint platform for the future a number of organizations are planning to move to the cloud and leverage SharePoint online for collaboration and enterprise content management. One of the powerful features in SharePoint 2013 (and SharePoint online) is the new search engine. When you start working with SharePoint online you will encounter a number of differences between how on-premises SharePoint and SharePoint online are administered. One of these is how you work with Managed Properties.
There are two types of properties in the SharePoint search schema: Managed and Crawled. “A crawled property is content and metadata that is extracted from an item, such as a document or a URL, during a crawl. To include the content and metadata of crawled properties in the search index, you map crawled properties to managed properties” (Reference article). In order to use managed properties, you can set some attributes on them such as queryable, refinable, sortable etc. One of the useful attributes is refinable. Once you set the property as refinable, it can then be added to the refinement panel in search thus allowing users to refine the data based on metadata that makes sense to them.
In SharePoint on-premises you can create managed properties from scratch and set these additional attributes. However, in SharePoint online you are limited on the type of attributes you can enable on new managed properties, for example, you cannot set the refinable property on new managed properties. To overcome this limitation, SharePoint online comes with pre-built managed properties such as RefinableString00 to RefinableString53, RefinableInt00 etc… You can use these properties to create new refinable managed properties. Don’t forget to set an Alias so you can use the alias in query strings to perform your queries instead of “RefinableString00”.
The following TechNet article will help you work through this: Managing the search schema