The spider hitch is a knot similar to the bimini twist. It creates a double in the line, which is easier to handle and tie. This also allows for stronger knots because a double line is stronger than a single strand of line when tied.
This is a very popular knot with big game anglers as it creates a very good shock absorber and has very similar attributes to the very popular bimini twist, but it is much easier and faster to tie. It is suitable for lines up to 15kg.
Personally I would always tie a bimini twist when I had plenty of time to get it right, but I have tied the spider hitch when rushed and it has performed quite well.
The reports I have read suggest it performs well for small sportsfish, but don't expect it to hold up with bigger game fish. For them you really should try to learn the bimini twist!
This video shows the process of tying a spider hitch very clearly - thanks to the creator of it!