Backline versus the PA
The PA is the sound system the audience hears: the main speakers, subwoofers and the mixing console out front. Backline is the equipment on stage that the band plays through — guitar and bass amplifiers, the drum kit, keyboards and their stands. Many venues and events supply the PA but not the backline, which is where bands get caught out.
What backline usually includes
Typically guitar amplifiers and cabinets, a bass amplifier and cabinet, a drum kit — often called a shell pack, with players bringing their own cymbals, snare and pedals — and keyboards with stands. Exactly what is shared and what each player brings should be agreed in advance, not discovered at soundcheck.
Microphones and DI
Vocals need microphones, and so do drums: a kick, a snare, toms and overheads at the least. Keyboards, acoustic guitars and anything electronic usually connect through a DI box, which converts their signal so it can travel cleanly to the console. A five-piece band with a miked kit is a lot of inputs, and every one needs checking.
Monitoring: what the band hears
The audience hears the PA. The band hears the monitors, and that decides whether they play well. Floor wedges are traditional; in-ear monitoring gives each performer their own mix and keeps the stage quieter, which makes the room easier to control. Which suits you depends on the band and the venue.
What to sort out before the day
Send a stage plot and an input list — who stands where, what they play, what needs a microphone or a DI. Agree which backline is supplied and which is brought. And build the line check into the schedule: a full band needs real time to check every input, and that should happen before guests arrive, not while they do.