merriam-webster.com defines* them this way:
A contest is a competition in which each contestant performs without direct contact with or interference from competitors.
A sweepstakes is any of various lotteries.
A giveaway is the act of giving something away free
*I chose the most relevant definition for our purposes.
So what does this mean for those of us who like to win and enter contests, sweepstakes and giveaways as a hobby?
In the sweeping world, there are two types of contests. For the most part, there is skill involved which makes them more difficult to enter than a simple entry sweepstakes and there will be fewer entrants so your odds of winning are better.
The first is a judged competition- it can be anything from a recipe contest to a photo contest to a writing contest or what have you. A single person or panel of judges use various guidelines to determine a score and judge accordingly. An example of this would be a writing contest that is awarded points based on various criteria: up to 50 points for relevance to theme, 20 points for humor, 20 points for grammar and 10 points for creativity or uniqueness.
The second is a voting contest, which is basically a popularity contest and quite frankly, I have only entered them on accident and am not overly fond of them as the best entry does not necessarily win. The entrants have to spend countless hours garnering votes and there are no guarantees no matter how good their entry. There is also a lot of cheating, presumed cheating and bad feelings that occur with this type of contest, some gets resolved fairly, and some the sponsors pretty much only care about getting visitors to their site and they don't care how you do it or if you follow the rules or not.
That being said, I do try to help out my fellow sweepers and bloggers and will vote for my friends and members of my communities IF I think they have a quality entry and I have the time.
Occasionally, you will find a contest that combines the two- either it is judged and the most popular are voted on or it is voted on and the most popular are then judged.
Sweepstakes are basically a bunch of people putting their name in the hat for a chance to win a prize or prizes and the winner(s) will be randomly chosen - no skill involved at all. Typically they are fairly easy to enter although now and then you will find one that has you answer a trivia question or two or play a matching game or something fairly easy and will generate a lot of entries because of their simplicity.
A giveaway is something someone gives away and can be done either randomly or based on some other criteria- a blogger can give something away to someone who follows their blog, a company can give a prize away on Twitter to whoever becomes their 1000th follower- basically anyone can give anything they like away for any reason and at this point there are far fewer laws and guidlines that have to be followed.
Which is right for you? That is a very personal decision- in my experience, if there is something I really want to win, it's worth taking the time to enter for, but I won't invest say 30 minutes in winning a $20 prize, but if it is a book I really want to read or free product I'd like to try I'm willing to put in the seconds or minutes required- the more I want it, the more effort I'll expend.
Do you enter contests, sweepstakes and/or giveaways? Which do you have more luck with? What are your favorite prizes to win?