What do you want?

There are four main things people can aim for when they start working out.
1. Size/Mass: For big muscles, use moderate to heavy weights with slow repetitions.
2. Definition: For a lean but well-toned body, do many repetitions using light weights.
3. Strength: To gain power, use heavy weights (close to your maximum) and go for less repetitions but with explosive movement.
4. Endurance/Stamina: One word – cardio. I would recommend swimming. Just keep swimming, swimming, swimming…
This isn't a one-or-the-other thing. You can have a mix of any two, or you can have all. It's better to aim for one of them first than try everything (like most beginners do) and get frustrated when not seeing results. It doesn't come easy. Not one of those things come easy, and that's why it's admirable. Not just because you look good but because you worked hard for it.