Softwood is a conifer (which tend to be evergreen) tree or wood that comes from a conifer tree — in other words, a tree that has “cones” containing seeds, and usually with needles that it keeps year-round. Examples include spruce, pine, redwood, cypress and other woods/trees commonly used for constructing musical instruments such as guitar and bass.
There is no correlation between a wood being technically classified as a softwood and the wood actually being “soft” or low density.