In jazz, what does "Front Line" refer to?

also, how does this relate to the rhythm section?

the front line refers to the musicians playing the lead parts in any particular configuration, which is everyone who is not in the rhythm section. the lead horns or singers stand on the front line and the bass, drums, and piano or guitar or other comping instrument are behind them.

traditionally the band is broken up into the front line, ( trumpets, sax and trombones etc) and the rhythm section ( guitar, bass, drums piano etc )