They contain spatial data for boundaries (counties, census tracts), roads, railroads, and rivers.
The most common use of "Tiger files" refers to (Topologically Integrated Geographic Encoding and Referencing) files. These are free, high-quality digital databases of geographic features across the U.S., used extensively in GIS (Geographic Information Systems) .
Downloading multiple files from TIGER FTP site - GIS StackExchange
Select your desired and geographic area (e.g., State or County).