Market timing is the practice of moving in and out of a market, an asset class, or a security based on predictions about future price direction — with the goal of buying before advances and selling before declines. It sits in contrast to a buy-and-hold approach, which accepts all market fluctuations in exchange for capturing the full long-run return.
The case against market timing is well-documented: the majority of the long-run equity return historically comes from a small number of extremely powerful up-days, and being out of the market on even a handful of those days reduces total returns significantly. The case for it — or at least for systematic, rules-based approaches — is that reducing the worst drawdowns may allow investors to stay invested through the cycle rather than panic-selling at the bottom.
The honest picture is that market timing works sometimes, for some strategies, in some market conditions — and fails in others. The goal of this site is to show you the methods, the signals, and their failure modes with interactive tools, so you can reach your own informed view rather than accept a dogmatic position in either direction.