Here's an online article from Lion of Zion Entertainment about the differences between a number of different types of Caribbean music:

"Frequently Asked Questions
History and Definition of Reggae

Question:

"Is there any possibility to get a description of the differences between Ska, Reggae, Dancehall, Rockers, Roots, Rocksteady etc...?"

Answer:

That is a very good question, there is a lot of confusion regarding the various types of reggae music. There are many different styles within the overall genre of reggae. Out of one root there are many branches.

Birthed in Jamaica in the late 50's this music was first an emulation of American rock and roll and rhythm and blues. The tempo of the music was fast and was created for dancing. Out of this emulation of American music mixed with African and Caribbean influences was birthed "ska". The Christafari song "Keep on Looking up" on our "Valley of Decision" album would be considered ska. In the sixties, as ska music progressed it evolved into a similar yet slower style called "rocksteady". The only significant difference between ska and rocksteady was the tempo, besides this, both styles had the famous Jamaican rhythm guitar and organ bubble complemented by drums, bass, horns, vocals and a groove that kept you moving.

As the music in Jamaica continued to evolve, it slowed down in tempo once again, giving birth to "reggae music". This is where there is some confusion. Many believe that reggae came first, however it is quite the contrary, reggae came third, after ska and rocksteady. "Reggae" was a phrase first coined by Toots and the Maytals and means "to the King" in Latin. The only other significant differences between reggae and its predecessors besides its tempo were its strong emphasis on a treble-less bottom end bass line, a one drop on the drums and its new spiritual emphasis in Rastafari. This reggae in its early or traditional state is what many now call "roots". This is by far one of the most infectious styles of the genre, made famous worldwide by Bob Marley.

Other styles that fit under the reggae genre include lover's rock. Lover's rock is an intimate roots music with a lyrical theme of love and relationships that was pioneered by such artists as Gregory Isaacs, Freddie McGregor and Dennis Brown. There is also another very popular style of reggae called "dub". In Jamaica whenever a song was released it was put out first as a single on a 7 inch record (what Americans call a 45). On the other side of this 7 inch was what is called the version, or the dub. In America today some would call it a sound track. It was the same song (often times with a different and psychedelic mix) that did not include the lead vocal.

Dubs were then taken to the dance halls and played next to the original version of the song. Then one Jamaican MC made history by talking, chatting and singing over the dub version of a song for his particular sound system (today this is known as a "special"). His name was Daddy U-Roy. This creative combination eventually birthed countless other musical styles. When this music reached its Jamaican counterparts then residing in New York it gave birth to what is now known as rap, or hip hop. Yes, you got it, rap was originally birthed in Jamaica out of reggae music!

However, in Jamaica this dub evolved into something different. People began reading poetry over these dub versions and it became "dub poetry". Made famous by such artists as Mutabaruka, Oko Onoura and Yasus Afari, dub poetry is still alive and strong today. By far the greatest child to be born out of this dub reggae is "dancehall". Often considered the sister of rap music, this music has been called many names such as "ragga", "dj style", "Jamaican rap" and the most popular "dancehall". This music began using traditional reggae rhythms and having artists rap (for lack of a better definition) in Jamaican Patois over the dub. This rapping is also known by other names such as "chatting", "chanting" or "toasting".

With dancehall came the computerization of reggae. These digital beats created a large gap between Dancehall and its predecessors. Originally made world famous by such artists as Shabba Ranks and Buju Banton, early versions of dancehall were often categorized as "slackness" (containing explicit sexual lyrics) or "gun talk" (containing violent lyrics). Since then dancehall has reached world wide fame by other artists such as Shaggy, Snow, Bounty Killer and even the Fugees. In the mid Nineties, dancehall again evolved turning from slackness and gun talk to conscious lyrics. With the conversion of Capleton and Buju Banton to Rastafari, many other artists began singing about Selassie instead of sex or guns.

Recently, dancehall has taken a turn to its foundation by going back to using standard roots rhythms. Accompanied by spiritual lyrics, artists such as Tony Rebel, Sizzla and Anthony B became famous singing Rastafarian lyrics over this new type of dancehall known as "culture".

Other types of music birthed from This large tree whose roots are ska are; "two tone ska" (from the U.K. in the 70's), the "third wave of ska" (an American hybrid of two tone ska, punk and hard edge alternative), "niyabingi" (tribal Africa and Jamaican hand drums accompanied by songs and chants of Rastafari), "jungle" (The U.K.'s hybrid of techno and dancehall), "drum and bass" (The second phase of jungle) and "ragga-hip hop" (a combination of dancehall and American hip hop).

Other Caribbean rhythms that are cousins of reggae/ska are "mento", "calypso" and "soca" just to name a few."

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