Nikon D3100 No autofocus motor?

I've read somewheres on the internet that the Nikon D3100 DSLR camera does not have an Autofocus motor and that a special type of lense is required to have it.
Does this mean the background in pictures won't be blurred unless I have those lenses?
If not, what does it mean?

"won't be blurred?" What does that mean? Yes DOF is a lens function but a focus motor has nothing to do with it.

Research some more. Since I'm not a Nikon guy I can't address your question directly so read some more, perhaps at the Nikon site.

All the auto-focus motors are in the lenses.

All Canon lenses have auto-focus motors in them. Only the USM lenses are ultra-fast auto-focusing

All the Nikon AF-S lenses have ultra-fast auto-focusing systems

I can't believe you think that you need an on-camera focusing motor to be able to use selective depth of field. They have NOTHING to do with each other

At this time, All the lenses you will ever need are available as AF-S lenses, which means you can forget about whether a camera has an in-camera focusing motor or not

What many don't seem to understand is that if you have Canon EF-S lenses, you will have to replace them once you graduate to a full frame Canon EOS 5D or 1D series camera. This is a concern to those who own a large number of EF-S Canon lenses and then upgrade to a full frame camera

Yes entry level Nikon dslr doesn't have auto focus motors and that means not all Nikon lens will work, you can still use it but you have to manually focus it, no autofocus.

The background blurr has no relation to this, you will get background no matter what type of lens you use, manual focus or autofocus no problem. I've a feeling you're referring to Bokeh! If you want that nice looking background blurr, you will need a special type of lens, anything below F2.8 lens will produce that.

Btw, at Canon dslr side, they have autofocus motor build in the lens so Canon all lens works.

Most every Nikon lens sold today is an AF-S lens that has a built-in autofocus motor. It is the *older* Nikon lenses (and certain uncommon specialty lenses) that may not have the autofocus motor; these lenses can still be used with the camera, but only as manual focus.

In general, the camera bodies that do have their own autofocus motors can focus much faster than those without.

Background blur (from shallow depth-of-field) is determined mainly by the aperture, not by the presence of a focus motor. Widening the aperture reduces depth of field, while also permitting more light through the lens. Lenses with longer focal lengths (telephoto) have wider apertures than those with shorter focal lengths (wide angle), and are thus better suited to blurring backgrounds.

Modern Nikon cameras use two distinct type of focus mechanism. Low end Nikon's use just and electronic link between the camera body and the lens, which means for auto-focus to function it needs to be built into the lens body. The more upmarket Nikon's feature both the electronic coupling and a screw/gear mechanical coupling where the motor is in the camera, the camera being able to use which ever mechanism in implemented on that particular lens. This means there's a greater range of lenses that will work with full functionality on the more expensive Nikons, but there are lenses that do pretty near everything available for your D3100. *Yes you can blur/de-focus the background.

I'm prepared to be wrong on this but I believe this is probably true for the upper-end Nikon's… The big advantage of having the motor built into the body, is the ability for the lens to perform a quick Auto-Focus, and then drop the clutch on the motor allowing the photographer to tweak the focus if they choose (DMF mode on Sony's). I only have one lens with the motor in the lens, and this is the function I Really miss when using it!

You don't need special lenses. Only AF-S and AF-I. They are in fact common and the de facto standard in Nikon crop sensor digital lenses.

http://www.kenrockwell.com/...s.htm#dslr

Blurring backgrounds does not depend on AF.

http://keerok-photography.blogspot.com/2011/05/how-to-blur-background.html