According to Wikipedia:

"Waiting for Tonight" is a song  originally written and recorded for American girl group 3rd Party's debut studio album, Alive (1997). Three years after the group disbanded, Jennifer Lopez recorded her own version of the song for her debut studio album, On the 6 (1999).

"Waiting for Tonight" is considered by various publications, such as Entertainment Weekly and the Chicago Tribune, to be the best song of Lopez's career (it's most certainly one of my favorites!).

Contemporary music critics have also credited the song with making her a leading artist in the dance-pop movement. It was used frequently as an anthem in anticipation for the new millennium.

The single was a commercial success, reaching the top ten in Australia, Finland, France, Italy, the Netherlands, New Zealand, Spain, the United Kingdom, and the United States.

"Waiting for Tonight" became Lopez's first song to top the US Billboard Hot Dance Club Songs chart. The song earned her a nomination for Best Dance Recording at the 42nd Annual Grammy Awards in 2000.

The accompanying music video for "Waiting for Tonight" was directed by Francis Lawrence and depicts a Y2K dance party. It was nominated for numerous awards, including two at the 2000 MTV Video Music Awards, where it won Best Dance Video.

"Waiting for Tonight" was documented and aired by MTV on Making the Video. On the show you saw Jennifer Lopez wearing stiletto heels and a micro-mini to perform a dance routine on a narrow, 6-foot-high Plexiglas platform while cameras caught her from every possible angle. Jennifer must not be afraid of heights.