"Impeachment' is a political charge.  It consists of whatever a simple majority of the House of Representatives votes it is.  If they say "Mopery and Dopery with intent to Grunge" is a "High Crime or Misdemeanor", that's "Impeachment"  

"'Conviction" of "Impeachment" is also a political verdict.  It exists if 67 (2/3) of the Senators vote "Guilty" to one or more "Articles of Impeachment" voted in by the House of Representatives.  

Thus endeth the civic lesson for today.