Some of this depends on where you are (Europe and the US is different in regards to some details e.g. what exactly you need to do to get your degree and if you do it in one program or in separate programs) but the fundamental difference is that a doctorat as in a PhD is a degree of a higher qualification than a Masters degree. Basically a doctorate is the next step after your masters.

You have to qualify yourself for both by contributing research in the form of a written thesis but the fundamental difference is how much work these works are: For doctorate, you have to write what in essence is a monograph, meaning a scientific book. It must contribute something completely new to research and usually ranges around 200 to 450 (sometimes more than that) pages of manuscript. A Masters Thesis is shorter than usually not exceeding 100 pages and while it is encouraged that it contributes something new to research, it is something not necessarily required.

In essence, a doctorate is higher and better qualification that enables you to pursue jobs at universities like tenure track positions.

In many American humanities programs, doctoral candidates earn an MA as part of their PhD course. In mine (in art history), you get your MA after your first two years in the program, when you "advance to candidacy." The first two years of an American PhD program are mostly coursework, with the following years devoted to developing, researching, and writing your dissertation. So, the MA is roughly equivalent to the first, easiest part of getting a PhD.

Put another way: an MA in most humanities fields takes at two years. A PhD takes at minimum six years, and often more like ten, depending on what kind of research travel (and in what languages) you have to carry out.

Ah I see. Thank you all for the responses I appreciate it!