An abstracting database prepares a summary of the core content of documents to enable users to determine whether or not they need to read the entire text. An abstract is a shortened version of the original piece. They are often accessible via a subscription and will be on a particular subject, or selection of subjects.
An indexing service analyses the content of documents and provides a guide to the information contained in them. It will contain subject terms and headings while also describing the content and main themes. An indexed document also enables users to locate the original.