Worshipful Master Elect 

The Worshipful Master Elect is a Master Mason, who after having served as either the JW, SW, or both, and who at least after the Masonic Year of 2008, at least in Pennsylvania, has reached a certain level of proficiency, who was elected to serve as Worshipful Master of a Lodge at the Election of Officers for the ensuing Masonic Year beginning of Saint Johns' Day Next.

After being elected he will be asked if he is willing to accept the Office of the Worshipful Master for the next year.  If he answers in the affirmative he will then be asked to agree to 15 charges before he can be installed as Worshipful Master of a Lodge.

During the installation of the Worshipful Master Elect to the Office of Worshipful Master only persons who have the Word of the Chair may be present.  The Worshipful Master Elect is given the Word of the Chair during the Installation ceremony.  All others must leave the open Lodge.  They will be readmitted after the installation.

I am not sure how this works with the new guidelines for Pennsylvania Freemasonry that were instituted at the beginning of 2010.

The Worshipful Master Elect will not officially take the Office of the Worshipful Master until Saint John's Day Next.