This has traditionally been interpreted as wronging a person with speech. It includes any statement that will embarrass, insult or deceive a person, or cause a person emotional pain or distress. Israel Meyer haKohen, better known as the Chafetz Chayim, wrote several books about lashon hara which all go into great detail. You are not to imply derogatory things about anyone. You are not to listen to derogatory things about anyone, and if you do, you're not to believe it.
Tale bearing is, essentially, any gossip.
The idea is that a talebearer is like a merchant whose merchandise is gossip or tale bearing. Some other terms that bring more understanding to the solemnity of this subject are avak rechilut or the dust of gossip and avak lashon hara, the dust of an evil tongue. Sometimes a violation of Torah can be committed in lashon hara, without even saying anything specific about another. Well, I suggest that you do, and draw your own conclusion regarding how really sound they are. The worst offense is motzi shem ra, or purposely spreading a bad name or lie about another, with the intention of bringing injury.