What's the difference between a magnifying glass and a loupe?

I would say a loupe is more pf a specialzed magnifying lass eg you may see things with a jewlers loupe you wouldnt pick up from a magnifying glass from a show bag.

A jeweler's loupe is a specialized magnifying glass used to inspect jewelry. Because magnification and clarity are essential to a good jeweler's loupe

A loupe (pronounced loop), is a type of magnification device used to see things one is looking at more closely. In this respect, they are simply a form of a modified microscope, allowing the user to be able to better apply the phenomenon of microscopy to his or her trade.

https://en.wikipedia.org/wiki/Loupe

A magnifying glass (called a hand lens in laboratory contexts) is a convex lens which is used to produce a magnified image of an object. The lens is usually mounted in a frame with a handle.

https://en.wikipedia.org/wiki/Magnifying_glass

I would say a loupe is more of a specialzed magnifying glass.

To clarify-- what's the structural difference, ie, what are the differences in the way the two are constructed, especially with regard to the way the lens(es) are set up?

"Three basic types of loupes exist. The first is a simple lens and results in the least amount of magnification. The second is the Galilean system which is composed of multiple lenses, which results in a higher degree of magnification. The last is the Prismatic loupe system which employs both lenses and prisms to reflect and focus light, resulting in the highest degree of magnification."

https://en.wikipedia.org/wiki/Loupe

What is commonly called a magnifying glass, also known as a hand lens, typically consists of a convex lens mounted in a frame with a straight handle on it, the whole looking somewhat similar to a hand mirror.

A loupe is generally a much smaller lens mounted in a metal cylinder with a hinged cover that swings to the side.

Photos:
http://kk.org/cooltools/cool-tools-2015-holiday-gift-guide-tools-under-10/
https://commons.wikimedia.org/wiki/File:Magnifying_glass_-_Faberge.jpg

Note: "Loupe" is French for "magnifying glass." In Spanish it's "lupa."
http://www.wordreference.com/enfr/magnifying+glass
http://www.wordreference.com/es/en/translation.asp?spen=lupa