These two words can be used very differently by people. For example, there are good bosses and bad ones. In addition, there are inspiring leaders and despotic ones! There is great fluidity, to say the least. So, it is not possible to give an answer. I can only give my opinion, but I will link a study on the flexibility of semantics. With that said, here is my opinion. A leader is sone who leads people, usually through foresight, vision and example. A boss is someone who has authority, but someone who does not necessarily lead.
The inspirational value cannot be overstated. The leader is one who seeks to develop power and strength from "the bottom up" and strives to inspire individuals to buy into a particular vision or goal. It is not that their power is any less, but they find it an essential part of their mission to be able to connect with others in the hopes of establishing a larger vision or paradigm. This is the critical difference, for a boss is more along the lines of someone who is in the position of power but rather conceives of it as something "top down." The boss is one who oversees, but is not as much of an inspirational figure. They wield power, but in the in final analysis are more of a short term figure as opposed to leader who could impact structural and long lasting conceptions of change.
Basically, the difference getween the two rests in the ability to inspire others to want to become leaders as well. A leader can rule over a boss, even if he or she were not in the position technically. This is known to happen in situations where a weak leader is mangled by his workers and eventually becomes removed.
An example I can give you is being a Principal. If a teacher with more leadership skills, organization skills and charisma begins to make rules for the Principal to follow and succeeds, then chances are that she would be the leader of the boss.
I have seen this myself, and the situation is not positive for any organization.
As the first answer states, the difference lies in the semantics. Generally, a boss is someone who has been designated to a position of authority over others. That designation does not mean, however, that a boss is a leader or even a respected individual because one can earn the title of boss through education, advantageous relationships, etc., without having any leadership potential.
A person can be a leader without having any official designation as such. Humans naturally follow people who inspire confidence (often unknowingly) or who command respect for various reasons (experience, attitude, eloquence). Of course, someone can be both a leader and a boss, but if someone has to choose which title he or she would prefer, I would guess that the answer would be "leader" because it carries a much more positive connotation than does "boss."
As far as origin goes, the word "leader" most likely comes from the word meaning "to travel" or "to go"; so it is easy to see how following someone who is willing to take the initiative (travel or go) would be perceived as an act of respect for that person's wisdom. In contrast, "boss" originates from the Dutch word for a master or male who holds a high position in a household. Because it is a term which breeds more familiarity than it does respect based on someone's actions or character, its modern, less positive connotation fits its origin.
Of course, these are not technical terms so there is not a technical answer to this. It is more of a matter of nuance.
These two words have very different connotations. The word leader has a much more positive connotation than boss.
A boss is just someone who has power, someone who tells everyone else what to do. A boss does not try to get consensus, does not try to inspire workers -- a boss just tells people what to do.
By contrast, a leader is more inspirational. A leader encourages people to do the things he or she wants rather than trying to force them.
So generally, it is said that a manager should be a leader rather than a boss so as to get better results.
The main difference between a leader and a boss is in the nature of power or influence they have over the actions of others. Leader have the power to lead and direct the action of their followers because of their ability to inspire confidence in them and motivate them. This authority is not handed down to them in line with some formal organizational design or company policy. It is the power they acquire by by their own behavior and performance.
In contrast the power of bosses or managers, in their capacity as bosses or managers, over their subordinates is formal, which is handed down to them in line with organizational design and company policies. The power they exercise over their subordinates is because the company has delegated to them some of the power they have over these employees because of their employment contracts. However it should be noted that a bosses may also be a good leader and may acquire additional influence over their subordinates using leadership qualities. As a matter of fact to be an effective boss, is necessary to become a good leader also.
In contras to some of the statements made in earlier posts, I do not believe that bosses are necessarily bad or ineffective. Just as there are good and bad leaders, there are good and bad bosses.