Reggae is an Afro-Caribbean style of music developed on the island of Jamaica. The origins can be found in traditional Afro-Caribbean music as well as US Rhythm & Blues. Ska and Rock Steady are 1960's precursors of reggae. Bob Marley, who later popularized the style on a world-wide basis, also recorded rock steady records early in his career. The style of reggae he made famous is called roots reggae and is still used by some artists as UB40 from the UK.
In Jamaica however, new styles are more popular, among them Lovers Rock and Raggamuffin. Dub is an instrumental sub-style of reggae. Mixing techniques employed in Dub probably influenced hip hop, Drum and Bass and other styles. In any case, the toasting or dee jaying of raggamuffin reggae - first used by artists such as Dillinger or Yellowman - had a world-wide impact because Jamaican DJ Kool Herc used them as he came up with a new style later called Hip hop or rap music. In the Jamaican sense of the word, a DJ is an MC or rapper, whereas the DJ is called selector in Jamaica. Therefore what is called dee jaying or chatting in Jamaica is called rapping in most other parts of the world.