Scalping is the trading style that aims for very small per-trade profits (a few ticks, a few cents) at very high frequency. Hundreds of trades per session is not unusual. The edge is in the math of the many — each trade pays a few dollars, compounded across volume.
The infrastructure requirements are non-negotiable. Per-share commissions need to be at the low end of the retail market (or you need direct-routing relationships); execution latency has to be measured in milliseconds; the bid-ask spread on your instruments has to be tight enough that crossing it doesn't eat the edge. Scalping a penny stock with a 5-cent spread is mathematically impossible regardless of skill.
Slippage is the silent killer. A 0.5-cent edge per trade vaporizes against 1-cent realized slippage. Scalpers who win do so by using limit orders almost exclusively, by knowing exactly which symbols their broker routes to which venues, and by avoiding the open and close where realized slippage is worst.
The psychological profile is unusual. You will be wrong constantly — 40-55% win rates are common — but the losses are small enough that the cumulative pain stays manageable if you stick to size. Discipline is enforced by the speed of the game; there isn't time to second-guess. The traders who scalp profitably tend to be the ones who treat each trade as completely independent and don't carry any emotional residue forward, which is a learnable skill but takes a year or more of journal review to develop.