A group of Freemasons forms a “lodge”. When three of such lodges decided to cooperate in 1717 London, they called this new organisation “Grand Lodge”. A place where a lodge resides is called an “orient” (Masonic jargon) and in an area some lodges may work together in a “Grand Orient” which falls under the national “Grand Lodge” (or no longer).
During history things started to run differently. Sometimes a Grand Lodge made a decision that made ‘London’ withdraw recognition. A few lodges of this Grand Lodge wanted to ‘stay with London’ and split off. Of course they cannot use the name Grand Lodge any longer, so they had to think of something else, “Grand Orient” for example, or either term with an addition of some sort, or something completely different.
The bottom line is, it is not like every “Grand Lodge” is regular and every “Grand Orient” is irregular. When you want to know the ‘status’ of a lodge or a Grand Lodge you will have to find out if it is regular or not. Internet is helpful in this regard. Most regular organisations will boast about this on their websites, but Wikipedia has helpful information. So, look around, ask around.