There are two types of methods that are utilized when learning to play or being taught to play the Trumpet. These two methods are the Conservatory Method and the Field Method. The default method for this application is the Field Method. Both of these methods are descibed below.

Field Method
(open note on bottom of partials)

Utilizing the Field Method of fingering, the open notes are located at the bottom of the partials instead of the top of the partials. Pretty much you could consider the Field Method as ad-hoc. In this method, there is no talk of tubing length or half or full steps, but rather just playing the notes clearly and concisely through practicing.

As you can tell by the description above, it does not have anything to deal with theory, but rather learning to play the notes. Because of this, the method is called the Field Method.

Conservatory Method
(open note on top of partials)

Utilizing the Conservatory Method of fingering, the open notes are located at the top of the partials instead of the bottom of the partials. By adjusting the tubing length of the trumpet (by selecting a valve) the tubing is extended which produces a lower pitch. When valve "1" is selected it increases the tubing length enough to lower the pitch by one whole step (or note), when valve "2" is selected it increases the tubing length enough to lower the pitch by one half step, and when valve "3" is selected it increases the tubing length enough to lower the pitch by one and a half steps. By selecting a combination of valves a complete series of notes are produced.

As you can tell by the description above, it has to deal a lot with theory and such. Which is mostly tought in a Conservatory. Because of this, the method is called the Conservatory Method.