Short answers, pulled from the story.
Marley Marl, born Marlon Lu'Ree Williams on the 30th of September, 1962, is an American DJ, record producer, rapper, and record label founder from Queensbridge, Queens. Vibe magazine credited him with having "forever changed the sound of hip-hop with his unique beat barrages," and he influenced artists including Biggie Smalls, RZA, DJ Premier, Pete Rock, and Madlib.
Marley Marl discovered sampling by accident during a studio session with an artist named Captain Rock at Unique Recording Studios in the early 1980s. While trying to pull a riff off a record, he accidentally captured an isolated snare hit and found it sounded better than the snare from his drum machine, a technique that became central to hip-hop production.
The Juice Crew is a hip-hop collective co-founded by Marley Marl and radio DJ Mr. Magic in 1983. Its members included Big Daddy Kane, Biz Markie, MC Shan, Roxanne Shante, Kool G Rap, and Craig G, and the collective was home to Cold Chillin' Records starting in 1986.
Marley Marl produced full albums for several Juice Crew members, including Big Daddy Kane's Long Live The Kane (1988), Biz Markie's Goin' Off (1988), MC Shan's Down By Law (1987) and Born to Be Wild (1988), Kool G Rap and DJ Polo's Road to the Riches (1989), Craig G's The Kingpin (1989), and Roxanne Shante's Bad Sister (1989).
Cold Chillin' Records was founded in 1986, and Marley Marl served as its in-house producer. He earned $250,000 per year for his production work there. In 1996 he filed a lawsuit against the label for unpaid royalties.
"Paid in Full" by Eric B. and Rakim was recorded in Marley Marl's studio, and he is credited as a featured contributor on the track from their debut album. The recording became one of the most studied and sampled songs in hip-hop history.