Hi,
Suffixes are optional letters at the end of a part number that specify certain device features. Sometimes it is used for Intel internal use only so you can ignore it, here 'X' indicates the 'PLLs in APEX™ and FLEX 10KE devices'.
Please refer the link below for more details,
https://www.intel.in/content/www/in/en/products/programmable/sample-ordering-codes.html
Regards,
Vicky
