PA28 Student Pilot confuses the phrase 'hold short' with the phrase 'position and hold' which results in a runway incursion on his first solo flight.

Narrative

This letter is about the runway incursion that happened this morning on my first solo flight. I'll try to explain what exactly happened. After I had done my run up checks I called Ground Control to ask for permission for taxi to the runway. When I received the clearance I went straight to the holding position at Runway 21. When I came to a stop (clear of the hold short line) I asked Tower for permission for right closed traffic and told him it was my first solo flight. He told me to hold short of Runway 21 and I responded with my reply that I would hold short on Runway 21. I actually thought he wanted me to taxi onto the runway and hold short on the runway; which was incorrect thinking on my part. I should have held short of the runway and waited for clearance to taxi onto the runway. I feel that the main reason for this mistake was that I didn't have a full understanding of the two phrases 'hold short' and 'position and hold;' even though I had heard these communications on previous dual flights. I was nervous for my first solo flight and maybe this played a small part in my decision making. I have since talked with my Flight Instructor and have reviewed the meaning of these phrases and I am confident that I will never make this mistake again. I am reviewing the 'Runway Safety' pamphlet published by the FAA to ensure that I follow proper taxi procedures in the future.