I see... So basically, negatives and positives are the same thing? Except for positives producing more vivid colors? If I bring a positives for development, do I need to tell the person any special instructions?
A positive is something you can see in true/real-life - like a printed photo. Red looks red, black looks black, white looks white.
A negative is a direct opposite. Red looks blue, black looks white, white looks black.
When you want to produce positives, also referred to as 'slides', 'transparencies' or 'trans' for short, you need to shoot on positive/slides/E-6 film. An exception as mentioned by Clown is specific Polaroid materials, but that's an exception and not a norm. I'm not sure if anyone still produces direct prints from trans anymore, but even if they do, such prints will cost a lot more than prints made from negatives.
When you want to product negatives for various reasons, primarily those being cheap and easy prints, or need wider latitude to color and exposure, shoot on negative film or those for C-41 processes.
Color positives are common. B&W trans are not common.
Both color and B&W negatives are common.
Most B&W negs require specific B&W chemistry for development.
Some B&W negs are C-41 compatible and can be developed at the usual processing and printing establishments that offer C-41 processes.
Some people choose to shoot on E6 material and have it cross-processed/X-processed in C-41 chemicals for weird and intense colors that are unrealistic. Only some labs will offer this service as it contaminates the chemicals.
'E-6' and C'41 and industry standard processing terminology for trans and begs respectively.