An ethernet PHY chip speed support
The first page of the datasheets says:


  
  Fully Compatible with 10/100/1000Base-T Networks
  Integrated MAC and 10Base-T PHY
  Supports One 10Base-T Port with Automatic Polarity Detection and Correction
  


So it's a 10 Mbit/s 10Base-T device but is compatible with the other standards so you can connect them together and get operation at the lower speed. 

You shouldn't rely on the search parameters that appear on supplier parametric search pages, they often seem to contain errors or information that is misleading.