A spey blade has a straight edge that sweeps up at the front to a short, rounded, almost blunt tip. It was ground for livestock work where a sharp point would do damage, and it survives today as the third blade on most traditional stockman patterns, where it is an excellent skinner and scraper.
Speying is a livestock procedure, and the blade was shaped so a stockman could work quickly without the point catching. The rounded tip and broad, shallow sweep both exist for that.
Almost nobody uses it for that now. It survived because the stockman pattern survived.
Skinning, because a rounded tip is far less likely to nick a hide than a fine one. Also scraping, spreading, and any job where you want edge without point.
On a stockman you get a clip point for piercing, a sheepsfoot for controlled cuts and a spey for skinning. That combination is a pocket-sized toolkit, which is why the pattern lasted.
Fully sharp along the edge. Only the point is rounded. People new to traditional knives sometimes assume a spey is a dull blade, and it is not.
See the glossary entry for the profile.