Although the use of terms is not consistent, “outcomes” usually refer to the results of your activities and whatever you are providing to clients (or whoever you are serving). The term “outputs” refers to all the goods and services you provide (information, assistance, training programs, food, etc.). Your outputs should lead directly to outcomes–doing something for a person should result in some change, or else it usually isn’t worth doing. For example, we provide information (an output) so that people know something they didn’t know before (an outcome). This outcome then leads to other outcomes, such as the capacity to do something with the information.
It is important to evaluate how you are performing your key activities and providing the goods and services. This is often referred to as “process” evaluation, focusing on how you are carrying out your mission. If there is a particular program model that you should be following (such as a set of standard practices mandated by a parent organization), this involves what is often called a “fidelity” evaluation, focusing on the extent to which the program model is being faithfully implemented.
Some evaluators distinguish between “outcomes” and “impacts.” Impacts usually refer to results that can be clearly attributed to the program. I think this is really a matter of degree, rather than a clear “either/or” distinction. If you are providing healthier food to someone who then changes her dietary habits, the change in behavior becomes an “impact” to the extent that you can demonstrate that the change would not have occurred without your program’s activities. It is very difficult to demonstrate or prove impact, so it usually makes more sense to talk in terms of outcomes, and try to find better ways to suggest that changes are due to the program. For example, careful use of comparison groups of people who are similar to your clients but did not participate in your program can strengthen your outcome evaluation.
However you think about evaluation, what is most important is to create a culture in your organization that fosters curiosity about whether you are making a difference, and begins to develop new ways to assess your performance and its effects.