Why do my pictures looks better on my camera?

I have a Nikon 31000 ( I think ) and I took a picture and it looked great on the camera screen. It was much much clearer on the camera than it was on my computer, it was also a lot brighter and on my computer I had to edit it to make it brighter. How come that happens? I know it might possibly be that it is more clearer on the screen because it's smaller and all that stuff with megapixels but I'm not really sure lol please explain I'm just some poor amateur.

There are some things you will eventually learn

1) The way a photo looks on a tiny 3 " LCD will look much different on a 17 inch or larger computer monitor.
2) You need to make sure that your computer monitor is calibrated and profiled at least once a month.
3) Make sure that you shoot at the cameras highest resolution, always
4) Make sure that the LCD is at the default settings.
5) Read your user manual and learn how to set the white balance.
6) Use this link to learn how to balance the ISO, shutter speed and lens aperture to produce near perfect exposures

http://camerasim.com/camera-simulator/

http://camerasim.com/slr-camera-explained/

Horselover,

You partially answered your own question about why images look different on your Nikon 3100 and on your PC screen - that is, the camera has a tiny display screen and you're seeing the images a lot larger when viewed on a computer monitor.

Some thoughts for you to keep in mind as you delve more into photography practice:

1- Don't base your impression of the success of a photo from the camera's display - it's small, you may have the brightness of the display set too bright (read your manual for how to tone it down) - use that display mostly to check the overall impression of the picture's composition rather than its exposure.
2- Activate the "Histogram" view in your camera (again, your handy dandy user manual will tell you how) and use it to gauge the general exposure of your shot. It will reflect the range of tones in your image. Read this for more background - but you can also Google the term and read or watch YouTube videos for tutorials: http://www.scribd.com/doc/71035446/127/Fixing-Exposures-with-Histograms
3- If your computer monitor is too bright or the colors are off on it it will affect how your images appear. That may not be important to you if you're mostly producing snapshots. But if you've invested in an entry level DSLR that implies you'd like to learn more about and be more serious about photography. To produce better end results if you're going to post-process (retouch) your photos, then you should calibrate your monitor (check out the Spyder 4 as less expensive than the ColorMunki option). Keep in mind that even your computer monitor may not look as crisp in reproducing your images as the data that was captured - depending on the resolution.
4- Shoot in Raw (or Raw + JPEG) to gather the most image data to work with in your post-processing work.

Lcd monitor and hd