Final answer:
Databases and indexes are secondary sources that provide access to materials on specific topics. Secondary sources rely on other sources and often cite and build upon primary sources. Tertiary sources summarize or digest information from primary and/or secondary sources.
Step-by-step explanation:
Databases and indexes are secondary sources which provide access to materials on specific topics. Secondary sources rely on sources other than direct observation or firsthand experience and often cite and build upon primary sources to provide perspective and analysis. Tertiary sources, on the other hand, summarize or digest information from primary and/or secondary sources and include reference materials such as encyclopedias and textbooks.