Simplify the following text for a Grade 6 native English-speaking person.
Original: Serena Jameka Williams , ( born September 26 , 1981 ) is an American current World No. 1 ranked female tennis player who has won twelve Grand Slam singles titles and an Olympic gold medal in women 's doubles .
Simplified: Serena Jameka Williams ( born September 26 , 1981 ) is an American professional tennis player who is a former World No. 1 and currently ranked World No. 10 in singles and No. 20 in doubles with sister Venus Williams . The Women 's Tennis Association has ranked her World No. 1 in singles on five separate occasions .