Color negative film is the kind of film usually found in convenience stores. It uses C-41 chemicals for processing, and you get negatives and prints from it when processed normally. Color negative film is very much “What you see is what you get” when it comes to coloration. It yields true-to-life colors and contrast, which is why it’s preferred by portrait and wedding photographers.
Color positive film (also called “reversal,” “slide,” or “transparency” film) uses E-6 chemicals for processing, and you get a positive image or “slides” from it when processed normally. When mounted on card stock, these are exactly like the slides that you’d put in a slide projector, or the slides that your grandparents have in boxes in the attic.
Now comes the tricky (but fun) part: when you use the C-41 chemicals (for your negative film) on your slide film, that’s called cross processing which yields the saturated, vivid colors and contrast that makes Lomographic images famous. Each slide film has different characteristics when cross-processed. Some films go red, others go blue, and some just get brighter with more contrast. You can study up on which films do what, but don’t expect to get the same results every time – there is nothing definite about the colors, they’re all mostly a surprise!