Short answers, pulled from the story.
Salsa music has its direct origins in the Son Montuno genre developed by Cuban musician Arsenio Rodriguez in the 1940s, rooted in the rural eastern Oriente province of Cuba, particularly Santiago de Cuba. Its core rhythms derive from the musical traditions brought to the Caribbean by West and Central African peoples, principally from the Kongo, Yoruba, and Bantu groups.
Fania Records was founded by Dominican musician Johnny Pacheco and Italian-American businessman Jerry Masucci in the late 1960s. The label introduced Willie Colón, Celia Cruz, Larry Harlow, Ray Barretto, Héctor Lavoe, and Ismael Miranda, and assembled the Fania All-Stars in 1968; by 1971 the All-Stars sold out Yankee Stadium.
Cheo Marquetti y su Conjunto - Los Salseros, formed in Cuba in 1955, is recognized as the first self-identified salsa band. The first album to carry the word salsa on its cover was released by La Sonora Habanera in 1957.
Tito Puente and Machito argued that the music labeled salsa was simply Cuban music that had been played for decades, rebranded for commercial purposes. Puente famously said "The only salsa I know is sold in a bottle called ketchup. I play Cuban music," and Machito stated it was "the same old music that was played in Cuba for over fifty years." Eventually both embraced the term as a financial necessity.
The clave is the foundational rhythmic instrument in salsa, typically played with two wooden sticks struck together. Every instrument in a salsa band either orients itself around the clave pattern or plays deliberately independent of it. The 3-2 and 2-3 Son claves are the most common of the four clave rhythms used in salsa.
Cuban son groups were broadcast on Radio Congo Belge in Léopoldville beginning in the 1940s, leading Congolese musicians to create their own Cuban-style compositions. The largest wave arrived as salsa, including the Fania All-Stars' 1974 concert at the 80,000-seat Stadu du Hai in Kinshasa. Since the mid-1990s, the super-group Africando has continued blending New York salsa with African artists including Salif Keita and Ismael Lo.