The laws of lashon harah are not stated clearly in the Torah nor in the gemora. In addition the distinction between lashon harah and rechilus is not made by the gemora but is made by rishonim such as the Rambam. My question is that the Rambam seems to state that simply talking about others is rechilus while the Chofetz Chaim says that it is only rechilus when a connection is made between the listener and what a 3rd party said about him or did something to him. There are other sources which indicate that rechilus is revealing the secrets of others (Mishna Sanhedrin 3:7) while Kesubos (46a) says it applies to slander.
Vayikra (19:16): Don't bear tales amongst your people and don't stand idly by the blood of others
Yerushalmi Peah (1:1): R Yishmael says that rechilus is lashon harah. It was taught in the name of R' Nechemiah that one should not be like a peddler who bears tales from one person to another.
However the Rambam makes a clear distinction between rechilus, lashon harah and slander
Rambam(Hilchos De’os 7:1-2): : 1) One who is talebearer about his fellow man transgresses a negative commandment as it says (Vayikra 19:16), Don’t be a talebearer amongst your people. This is a very great sin and it has caused many people to be killed amongst Israel. That is why is adjacent to “Don’t stand idly by the blood of your fellow.” Go and learn what happened to Doeg. 2)What is a rachil? It is a person who bears tales and goes from one person to another and he says this is what so and so said or this is what I heard about so and so. And even though what he says is true it destroys the world. There is a much greater sin then this and is included in this prohibition of rechilas (Vayikra 19:16) and that is lashon harah. It is someone saying negative things about others – even though the information is true. However if he says lies about others it is called motzi shem rah (slander) on others. But the one who speaks lashon harah regularly (baal lashon harah) is one who sits and says this is what so and so did and his ancestors were so and so or this is what I heard about him – and what he says is negative. The verse regarding this is Tehilim (12:4), The L-rd shall cut off all flattering lips, and the tongue that speaks arrogant things
In contrast the Chofetz Chaim limits rechilus to reporting information that another did to the person being told the rechilus. The Rambam make no such an assertion and obviously neither did the Talmud
Chofetz Chaim (Hilchos Rechilos 1:2): What is a rachil? It is a person who bears tales from one person to another and he goes and says, “This is what so and so said about you or this is what so and so did to you or this is what I heard about him that he did to you or he wants to do to you. Even if the information is not negative about the one he is speaking and even though according to the rachil if the person had been asked directly he would not deny the information either because what he did or said was appropriate or because his intent in his action or words were different – nevertheless he is called a rachil.
However the Kesef Mishna claims that that is what the Rambam meant by citing Doeg.
Kesef Mishna (Hilchos De'os 7:1): One who bears tales about others – The view of the Rambam is that a rachil is one who say, that so and so said this about you or that he did something to you – even though the information is not negative about the one being talked about as we see regarding Do’eg who said that Achimelech gave bread and the sword of Goliath to Dovid and if he had been asked he would not have denied it because he didn’t view this as something negative and in fact the opposite was true in that he thought he was serving Shaul by his actions as he himself said.