First thing's first, while some brands market their silk lashes as 100% silk lashes, they are a synthetic based silk fibre, not actually real silk, as real silk is quite a soft material and won't be able to hold its shape and curl. Depending on whether this is important to you, you'll want to do some research to find out what kind of synthetic fibre the lash brand is actually using.
"Silk" lashes are a newer type of lashes that have come out in recent years, that's finer and more natural looking than the traditional faux mink eyelashes. Although sometimes, it seems the terms are used interchangeably, and look wise, they could be quite similar.
Silk lashes are not made with real silk, they're made with a synthetic material