Maximum drawdown
Maximum drawdown is the largest peak-to-trough drop recorded over the whole life of a trading history.
It is one of the key figures in a track record. It shows the worst period the strategy went through and gives you an idea of what you must be ready to endure if you follow it.
Never read it on its own: a 40% return with a 50% maximum drawdown is far more worrying than a 15% return with an 8% drawdown. The ratio between the two is a good first filter.
Past maximum drawdown is not a ceiling. The worst is often still ahead. Build in a safety margin, and at a prop firm, keep well clear of the overall loss limit set by the challenge.