The S3 looks like a DSLR which adds to the confusion for a lot of people.
There are a couple of important differences. I guess the main one is the ability to swap lenses, owning multiple lenses for an SLR camera is not cheap, but it can make a huge difference.
Another difference is that with an SLR when you look through the viewfinder you see a live image, this is essential for sports shooting, where if you see something happen you can capture it instantly, not a fraction of a second later when the moment has passed. DSLR's are also much faster, mine takes 3 full resolution shots per second which is slow these days!
DSLR sensors are usually much larger than compact which helps with factors like noise and sharpness.

That said, the most important factors when making pictures are things like composition, timing and colour, a good eye for a picture will outweigh any equipment benefits. You will mostly be able to take the same pictures as anybody else and it will be rare that your camera gets in the way of a good photo.

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