A Masonic Lodge is the basic organization of Freemasonry.  Every new Lodge must be warranted by a Grand Lodge, but is subject to its direction only in enforcing the published Constitution of the jurisdiction.  A Master Freemason is generally entitled to visit any Lodge in any jurisdiction in amity with his own.  He is first usually required to check, and certify, the regularity of the relationship of the Lodge and be able to satisfy that Lodge of his regularity of membership. Freemasons gather together as a Lodge to work the three basic Degrees of Entered Apprentice, Fellowcraft and Master Mason.  Freemasons meet as a Lodge not in a Lodge, although Masonic premises may be called Lodges, as well as Temples ("of Philosophy and the Arts").  In many countries Masonic Centre or Hall has now replaced these terms to avoid arousing prejudice and suspicion.  Several different Lodges, or other Masonic organizations, often use the same premises at different times.

Blue Lodges, Craft Lodges or Ancient Craft Lodges refer to the lodges that work the first three Masonic degrees, rather than the appendant Masonic orders Masonic orders such as York Rite and Scottish Rite. The term "Craft Lodge" is used in Great Britain. The Blue Lodge is said to refer to the traditional colour of regalia in Lodges derived from English or Irish Freemasonry. Although the term was originally frowned upon, it has gained widespread and mainstream usage in America in recent times.

(portions of this introduction taken from Wikipedia)