Traditionally, steel-string guitars have been made of a combination of various tonewoods, or woods considered to have pleasing resonant qualities when used in instrument-making. The term is ill-defined and the wood species that are considered tonewoods have evolved throughout history.
Traditionally, steel-string guitars have been constructed using a blend of different types of wood, often chosen for their resonance qualities.  The concept of "tonewood" is not clearly defined and has changed over time.