A bankroll is money set aside exclusively for betting — an amount whose complete loss you could absorb without harm. Bankroll management is the set of rules governing how much of it any single bet may risk. Common approaches: flat staking (the same fixed unit every time), percentage staking (a fixed share of the current bankroll), or Kelly-based staking scaled to edge.
The purpose is survival through variance. Even a genuinely profitable strategy hits losing runs of ten or more bets; staking too large turns a normal downswing into ruin before the edge can express itself. Most disciplined bettors risk 1–2% of bankroll per bet. Just as important: never top up a bankroll to chase losses — that is the failure mode that turns betting from entertainment into a problem.
With a £500 bankroll and 1.5% flat stakes (£7.50 per bet), a brutal 15-bet losing streak costs £112.50 — painful but survivable, leaving 77% of the fund intact.