1RM, an estimate
Your current benchmark is a recent set taken to failure, from 1 to 12 reps. It gives your 1RM, the heaviest load you can lift once.
Each formula gives its own estimate, and the most accurate one depends on the exercise, sex and training level. Beyond 12 reps, they become unreliable.
Above 100%: loads for eccentric work and partial movements.
Percentages are only one way to set a load. RPE, reps in reserve, bar velocity: explore them on tafdoc.