One heres no end of "what Is ethics?" and endless debates over what one "should" do and why?, and "are these things objective or subjective?" and "can we even deceide all our actions anyway?" Naturally as the "idea" of ethics (not the ethics themselves obviously) is a human creation, summing up ethics is a difficult things to do as it has been created from conflicting sources...but I think aristotle was onto something when he went into "Virtue Ethics". I tend to use that in combination with biology and basic psychology to work out my ethical questions, and thus here is what I think ethics is in a nutshell:

"Ethics is an inescapable result of our being a social species, and you see it in almost all of the animal kingdom. It is, in its most basic sense a recognition that other creatures exist, and a self set or accepted set of rules to act accordingly. The purpose being, to floorish, in a social environment. For wolf packs have strict rules, the alpha male only has authority over other males, the females fall under the alpha female's guidance and vice versa, also it is only the alpha pair that are aloud to mate, and only each other. If a wolf breaks the rules, they can be assulted even killed or banished from the group. In order to floorish and prosper, a wolf must accept the rules of wolf society, to recognise that other wolves exist. Humans are similar, but with much more complicated rules. Some of our rules are enforced more than others, the most serious being called "laws". Laws are in place to make sure everyone plays "fair", so that nobody takes advantage of each other, because if the human team or society is to prosper, we need to work togethar and that cannot be done if we are raping, stealing from and murdering each other. However, law only covers the rules of mere practical ethics, the more personal kind is largely left to individuals. For example, adultery is not illegal (at least in my country) because it isn't totally impractical for all society to have it around, I would however still call it immoral (unless its consentual), and that is because of a lack of virtue.
Virtues are the tools we utilise in order to apply our actions around others for the best results. So virtues like compassion, generosity, courage, happiness, loyalty etc, these all go down well in a social environment, and if someone deliberately ignores them they end up shuned, possibly assulted and even killed, just like with wolves. What can also result in this is if the moral agent utilises too much of any one virtue. Too little courage is cowardice, but too much is fool hardiness. Too little generosity is greedy, but too much can be suffocating. Too little compassion is callous, but too much is masochistic, too little loyalty is selfish, but too much is sycophantic...etc In order to get the best results and to make the most people happy one must find a balance of all one's virtues and be accepted as an "all-round-decent-human-being". Now none of this, has anything to do with "moral worthiness" which is non-existent in my opinion. People do moral or immoral (or amoral) acts because of their genetic profile and their past environment, its not their fault. This doesn't change the fact that we should praise people to allow them to associate good behaviour with good results, and to punish people to associate bad behaviour with bad results for this is basic behaviour psychology, listen to Pavlov! Also the use of the word "should", should not be made out of context really (although I do it all the time). "Should" only really makes sense if you say "should IF", for example IF you want to succeed in x, then you "should" do y. "Should" means, this will make x most likely. So that is it, we need to work togethar because that is what humanity does, it forms societies and groups, but in order to work togethar we need to respect each other's needs and drives and compromise with each other, so to that end we invent systems of rules that allow us to do this, the rules we call values, and the psychological tools we use to reach these values, we call virtues.