Often times when you don't take an interest in a particular subject most will group different genres into the same category. This is especially true for photography, for example swimwear, glamour, boudoir, fashion and even pinup, to some might appear to be the same and while the style and look of some of these images can be difficult to categorize, it's the overall purpose of the images that will set them apart.
In the case of Glamour vs Boudoir, even an individual Google search will deliver some very similar image results, so let's start with how they are defined.
Glamour
noun
1. the quality of fascinating, alluring, or attracting, especially by a combination of charm and good looks.
2. excitement, adventure, and unusual activity: the glamour of being an explorer.
3. magic or enchantment; spell; witchery.
adjective
4. suggestive or full of glamour; glamorous: a glamour job in television; glamour stocks.
Boudoir
noun
1. a woman's bedroom or private sitting room.
Though often crossing over into glamour, the genre of boudoir photography is not just about the final image(s) created, but about the premise behind why someone opts to hire a boudoir photographer as well as who the images are intended for, which can vary. Boudoir is similar to glamour but is often about showcasing fantasy that is often steeped very much in reality, as these images are very often gifts for significant others or for the clients own benefit. Commercially the genre is often (though not exclusively) derived from a market for brides to surprise their future husbands by gifting the images on or before their wedding day. Other motivations or inspiration for boudoir photography shoots include anniversaries, birthdays, Valentine's Day, weight loss celebrations, other forms of body change or alteration (such as breast augmentation or reduction) and for servicemen and women overseas. For a brief moment in time, a boudoir client is a glamour model, in front of the camera, creating fantasy.