One of the dictionary definitions of happiness is "pleasure" (www.dictionary.com) or "a pleasurable experience" (Merriam-Webster online dictionary). A lot of times, we substitute these two concepts one for another. Happiness is defined by feeling pleasure. And conversely, whatever brings us pleasure, makes us happy. It seems that pleasures are the stepping stones to happiness, and we are chasing pleasures believing that we are looking for happiness.
In fact, these two are not at all the same, and in our pursuit of happiness, we have to recognize their difference.
Let's consider everyday examples of what might bring us pleasure. To eat a good meal is a pleasure. To watch a movie. To enter air conditioned building on a hot day. But do these things make us happy? And I mean really happy - not feeling good for a while, but knowing that we are happy individuals?
The Dalai Lama in his book "The Way to Freedom" writes that pleasure is replacing one kind of suffering by another kind of suffering. For example, you stand for a long time and you are tired, so when you sit down; it's a pleasure. But as you continue sitting down, you will find that you feel uncomfortable, and now you want to stand up, run a little, walk around. If you are hungry, to eat is a pleasure indeed. But if you keep eating past the point where you feel full, it will become unpleasant. When you are hot - you derive pleasure from cooling down. But you get cold in a while, and yearn for warmth. You get the idea. The pleasures we crave are actually the very beginnings of suffering of one kind or another. If we keep doing and doing the things that bring us pleasure, they will not be pleasurable for long. That proves the wisdom that everything is good in moderation only. That also contradicts the notion of lasting happiness.
The other observation that helps distinguish happiness from pleasure is that pleasure is something that mostly comes from the outside sources. It's the food, the climate, the money, friends, technology etc. that bring us pleasure. And these pleasurable occurrences only bring us pleasure as they happen. As soon as we do not get the next scheduled meal, enough money, or the friends leave, the pleasure rapidly subsides. Happiness is something that comes from within us. It is a lasting feeling that ideally does not depend on the food, the climate, the money, friends, technology, etc.
Pleasures are fleeting, while happiness is a sustainable constant within us.
This is not to devalue pleasures. Truly, they are great! (Well, most of the time.) But we have to be able to clearly distinguish between the two ideas, and not mix one for the other. When we've separated the concepts of happiness and pleasure, we become one step closer to understanding what happiness is and what it consists of.