When you start this journey you are going to be bombarded with tons of information about which workout is better for your body, which gives you abs, and which is best for fat loss. In reality the best exercise you can do is one you truly enjoy, and causes your heart rate to go up. Do not allow yourself to become overwhelmed. Experts will never agree which is right but the tried and truest weight loss is achieved using cardio. Cardio burns calories while burning fat.
For the best FAT burn you should work at 70-90% of your maximum heart rate, but to be within the Fitness Zone or Fat Burn Zone you only need to be at about 60-70% of your maximum heart rate.
The difference here is anything above 60% is burning calories and some fat but burning above 70% guarantees maximum calorie and fat burn. And maximum fat burn is what you want. However if exercise is new to you, do not push for the max. Start slow and build endurance or you risk getting injured or burning out.
Another great method for burning fat is with High Intensity Interval Training, out HIIT. This is a few second of max heart rate followed by a couple of minutes in the Fitness Zone. HIIT is also a great way to help build endurance.
Now while cardio does help lose weight and burn fat it does nothing for getting that 'toned' look. To lose weight while toning you really need to incorporate weight training. And ladies there is no reason to fear weights, you will not bulk up unless you are trying to. By using low weights high reps you tone the muscle and surrounding skin without building the muscle up. You also burn more calories the more muscular you are because muscle burns more calories than fat.
If you gave already built some endurance you should look into circuit training. This is a serious of workouts that include HIIT as well as weights, all in one session. This alloyed for max burn while toning. Great way to tighten up. I highly recommend Jillian Michaels 30 Day Shred. It has three levels, one being the easiest. I have made it through the first two levels, about to begin three. It is hard, you will sweat, but it is rewarding in the end. She also shows modifications for the more intense moved if you have injuries, out if you just aren't there yet. You can find it cheap online and at most department stores.
And again I reiterate how important it is to hat a great rate monitor that calculates calories burned.
Now go out there, find what you love, and get moving!