Many people want to improve their physical fitness, and there are many ways to achieve that. However, it is often easy to confuse true structured exercise with simply being active. If you want to improve your physical fitness, just being active is not enough.
Exercise is a physical activity that is planned, structured, repetitive, and purposeful. Physical activity simply includes any body movement that contracts your muscles to burn more calories than your body would normally do to just to exist at rest.
While everyday physical activities such as performing housework, walking, or taking a hike keep your body moving and still count toward your weekly activity, it will not generally allow you to reap all the benefits that come from a structured exercise program.
Adding a well designed exercise program to your normal daily activities is the best combination to be successful, no matter what your specific goals may be. Simply being "active" is a great adjunct to a well rounded exercise routine, but should not be solely relied on to see fitness improvements.
If you are new to exercising, I would suggest starting with a trainer who can tailor a specific program to your individual goals. As you progress, a trainer will be able to make adjustments to your program to allow for the maximum efficacy and avoid plateaus.