The word Softshell is used on a broad range of products. The common factor with these products is that two fabrics with different properties are combined to create a material with special qualities. The most common thing is that one wishes to create a soft interior that binds and draws off moisture, and an outside that resists wind, rain, and wear-and-tear.
Softshell jackets are made of a smooth-faced, stretchy, tightly-woven fabric that usually consists of nylon blended with elastane. They are renowned for their unrestrictive range of motion, body-hugging fit, superb breathability, wind and water resistance (to varying degrees) and often stylish appearance. After emerging a decade or so ago, softshells quickly became a popular alternative to traditional hardshell jackets (principally GORE-TEX jackets at the time), as well as fleece garments like Polartec Classic jackets.
Can a softshell replace your trusty hardshell in sustained rain or snowfall? Probably not. What softshells do best is keep you warm and dry while your heart rate is up in windy and/or damp weather.