Summary
When used with the Describe function, a file returns a dataType of "File".
Code sample
The following stand-alone script displays some Describe Object Properties for a file.
import arcpy
# Create a Describe object
#
desc = arcpy.Describe("C:/data/Install.log")
# Print some Describe Object properties for the file
#
print("Data Type: " + desc.dataType)
print("Path: " + desc.path)
print("Base Name: " + desc.baseName)
print("Extension: " + desc.extension)