Pixels:
A pixel is a single dot in an image. Pixels are what makes an image become an image, basically puts the image together this is because the pixels are so close together that it looks like they are connected, this is based on DPI.
DPI is short for Dots Per Inch, this is basically the dots in the image that bring out the image for thr printer to print it out correctly. A printer that may have 600 DPI is a printer that can print 600 x 600 per square inch or 360,000 dots per inch. The more pixels, the higher the resolution, simple! Or it sounds it. All pixels have a colour, thats how in an image, the colour comes through by pixels.

Another word for pixel is Picture Element

 

The Definition of an Image:

 

The word definition is used in a few things but is mostly common and used for TV (High Definition TV). The 'definition' of the arrow shown above is 26X16, definition is all about the number of elements that create the image.

The fewer the pixel in an image, the more blurry/fuzzy it will become, for an identical subject, more pixels is better

 

Resolution:

Resolution is the number of pixels per mm, the computer screen you are looking at right now is set at a particular resolution. The bigger your screen, the bigger it is that the resolution will be set to.
 xox