I recently was asked this question from a newer whittler. I observed his whittling and noticed his knife. This fellows knife had an "up-sweep" blade referred by most as a scimitar shape. Like this:
While this blade is a wonderful shape, it may present a problem for the newer whittler, that can result in some "fuzzies". While the blade shape facilitates a slicing motion to ones cuts it can require an additional motion when removing a corner chip. This may be particularly evident when removing a chip to form an eye area.
After some whittling experience the scimitar knife technique will become second nature, but I recommend that a new whittler may find more success with a straight blade.