Trading frequency is a measure of how often a trader or strategy enters and exits positions. It is usually expressed through the typical holding period or the number of trades in a given time. Strategies are loosely grouped into three bands. High-frequency trading holds positions for fractions of a second to minutes and trades thousands of times a day. Medium-frequency trading holds for minutes to days. Low-frequency trading holds for weeks or months. The boundaries are conventions, not formal definitions.
Frequency shapes almost every other feature of a strategy. Faster strategies earn a small amount per trade, so each transaction cost and delay matters and investment in low latency technology is essential. They can deploy only limited capital. Slower strategies tolerate ordinary infrastructure and can manage far larger sums, but produce fewer independent trades, so more years are needed to judge whether results reflect skill.