its for a school assignment, the internet has soooo much information that all seems to contradict each other! any help would be great thanks

The difference is in how long you can expect to lose the weight for. Weight loss pills deal with the symptom of the real problem, they generally fall into three categories:
1. Metabolism boosters
2. Appetite suppressants
3. Fat blockers
If someone takes a pill to deal with appetite for example, they will also need to deal with the reason why their body feels it needs more food. Eventually if your body is eating less than it needs your health will suffer and then your metabolism will slow.
Boosting metabolism is generally dangerous with many drugs taken off the market as when you elevate metabolic rate your heart rate, respiration, blood pressure all increase putting more pressure on your system.
If the patient doesn't deal with the diet and lifestyle factors and just takes the drug their will be an initial drop in weight but usually results in a weight increase when the body's desire to normalise function gets too great for the drug to cope with.
2/3rds of people who lose weight will be back to their same weight or heavier after 3 years, long term weight loss only comes with dealing with the problem. Drugs could be used to help make the required changes initially but then needs to take a back seat to good old fashioned diet and exercise.
Brett
http://www.homefitnesstrainer.com.au

Good: They make you feel like you're doing something about your weight.
Bad: They don't work. Ever. And many times can harm your health. Look up Fen-Phen. (Not sure of spelling). Caused healthy people to die of heart problems.