What kind of a camera is the nikon 1 J1?

It has interchangeable lenses but no viewfinder.It's not a point & shoot but it's not a digital SLR either. What is it?

It is a member of a new bread of cameras just introduced by manufacturers.

It's designations is "Mirrorless"

Rather concern your self on the proper name at this time, I would heed the advise of other "pro's" on this subject and take a "wait and see" attitude on the popularity and longevity of this product, before committing to making a purchase.

Lots of us refer to them as EVIL cameras (Electronic Viewfinder Interchangeable Lenses). Actually they're nothing more than a glorified, way over rated and way over price point and shoot that changes
lenses.

We're now beginning to see forum entries like "okay, where can I now buy a 'real' camera"?

They are kind of in-between a point & shoot and DSLR.

These types of cameras are typically called CSC - Compact System Cameras; although MILC = mirrorless interchangeable lens camera, and Evil - electric viewfinder interchangeable lens - is often used to describe them.

Quality-wise, these cameras can approach entry-level DSLR performance (as in the case of Sony NEX - as they have the same size sensors), but at any rate, they all perform above the typical point-and-shoot, as they all have significantly larger sensors than point & shoots (except for the Pentax Q, which has the same small sensor as point & shoots).

The Nikon 1 cameras have smaller sensors than most CSC cameras, but the cameras are actually designed quite well, and fall somewhere in the mid level; about par with micro 4/3rds cameras, but not quite as good as NEX.

The V1 though does have an electronic viewfinder, so it is an upgrade of the J1.

The target for these cameras is for someone wanting better performance than a point and shoot, but do not want to lug around a heavy DSLR; and are willing to accept a bit more convenience due to the smaller package than the superior performance of a DSLR.

However, there's one Achilles Heel to these cameras. Once you start buying additional lenses and accessories, they quickly begin to cost as much as DSLRs, with less performance.

I have a Nikon V1, simply to augment my DSLRs. If I need a lot of reach, I can use an FT1 adapter, which will allow me to use my DSLR lenses on the V1. I have a Tokina 80-400mm lens, and when used on the Nikon V1, it is equivalent to a 1080mm lens. Or if I use my 80-200mm f/2.8, it is equivalent to a 540mm lens at f/2.8 (there's no light restriction as there's with using teleconverters).

While there are a few downsides to using such adapter; AF-S lenses will autofocus, but AF lenses will not, having to use spot focusing, and a few others, for a second camera, it certainly beats a bridge camera with long zoom lens (larger sensor, higher performance lens).

And given that you can buy a Nikon V1 right now with a 10-30mm kit lens for $299 (until the end of Dec), it may be an attractive buy, especially given the original MSRP was a way overpriced $899.

It was called a hybrid before then subcategorized as a mirrorless interchangeable lens camera (MILC). The term used nowadays is compact system camera (CSC) with some sticking simply to mirrorless.

The ever changing terms are there because there's no standard to these sort of cameras. Some have the SLR hump but with an electronic viewfinder (EVF) while some rely only on the rear LCD. Some look like flattened dSLR's while some resemble point-and-shoot (PNS) cameras with oversized lenses. What is common though is that they all have an interchangeable lens mount system. The micro four-thirds system is the most popular with around a handful of brands committing to it. The problem is that almost all of these cameras use a lens mount that is different from their dSLR lens mount so lenses aren't interchangeable among their two systems limiting the lens options to the mirrorless system. That is with exception to Pentax K-01.