From Diablo Wiki
Softcore refers to "normal" play mode, where characters can die without permanent character loss. This is not an official term for the character/game type, and is used simply to differentiate between hardcore mode, where death results in permanent character loss.
Some non-Hardcore players take offense at the term, and some Hardcore players mean it to be insulting or dismissive, but generally the term is simply used to make clear the game type, without any pejorative connotation.
- See more Reference terms.