The description of inclusive production of single unpolarized light hadrons using fragmentation functions in the framework of the factorization theorem is reviewed. The factorization of observables into perturbatively calculable quantities and these universal fragmentation functions are summarized and some improvements beyond the standard fixed order approach are discussed. The extraction of fragmentation functions for light charged (${\pi }^{\pm }$, $K^{\pm }$, and $p∕\overline{p}$) and neutral ($K_S^0$ and $\Lambda ∕\overline{\Lambda }$) hadrons using these theoretical tools is discussed through global fits to experimental data from reactions at various colliders, in particular from accurate $e^{+}{e}^{-}$ reactions at the Large Electron-Position Collider (LEP), and the subsequent successful predictions of other experimental data, such as data gathered at Hadron Electron Ring Accelerator (HERA), the Tevatron, and the Relativistic Heavy Ion Collider (RHIC), from these fitted fragmentation functions as allowed by factorization universality. These global fits also impose competitive constraints on ${\alpha }_s\left(M_Z\right)$. Emphasis is placed on the need for accurate data from $pp\left(\overline{p}\right)$ and $ep$ reactions in which the hadron species is identified in order to constrain the separate fragmentation functions of the gluon and each quark flavor for each hadron species.

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