Color Theory defines a True Shade as any pure Hue or mixture of pure colors with only Black added. In other words, it contains absolutely no White or Gray.
A Shade darkens the color. It remains the same Hue only a darker version. As has been noted above, even a small amount of White or Gray added to a color, transforms it into a Tone.
Therefore a Shade can range from slightly darker than your original color, all the way to nearly Black with barely any of the color mixed in.
Credit: Color Wheel Artist