Without grip, you won't change direction.
If your objective is to carve cleans tracks. You'll need to eliminate any sideways slippage of the ski, so the ski's design creates a direction change as they glide forward through the snow.
On the other hand, a steered turn involves a blend of grip and slip. Otherwise, you'll be locked into a carve, making it difficult to twist the skis effectively.
Having the ability to do both is crucial to being a versatile skier. So what determines whether a ski grips or slips?
First, we need to acknowledge that the working ski has to dig into the snow and cut a platform that will support you.
In soft snow, this is a pretty easy task as the snow compresses and supports the entire base of the ski. On hard snow, there will need to be enough downward force on the working ski, and the edges may need to be sharp enough to penetrate the snow.

The ski must dig into the snow and create a platform for support.

Soft snow pushes back on the entire base of the ski.

On hard the snow, downward force is concentrated on a fine edge.
A good rule of thumb is to balance through the middle of the outside, which should allow for the optimal downward gripping forces to be applied to the ski.
The other crucial element is the ski's 'Platform Angle'. In order to hold, the base of the ski needs to be perpendicular to the force applied to it. Otherwise, the skier's platform slopes away, and the ski will slip sideways.


Ski Grips - Base of ski held perpendicular to forces

Ski Slips - Platfrom angle of more than 90 degrees
Varying Turn Shape & Platform Angle vs Edge Angle
There are a few ways we can adjust turn shape.
Most people instinctively think of a rotational move, twisting their skis further across their momentum to tighten the arc. As mentioned above, this twisting action often requires a little less grip and more slip. However, the ski also has its own built-in steering angle... and this is affected through "Edge Angle"
"Edge Angle" refers to the angle between the base of the ski and the snow surface. The higher the edge angle, the more the ski will bend.
In summary, reaching a critical "Platform Angle" will allow the ski to grip, whereas "Edge Angle", will determine how much bend is created by the ski's sidecut and, therefore, how tight the arc will be carved.

"Edge Angle" between the base and the snow surface.

Higher 'Edge Angle' creates more bend in the ski
Got it, so to manage grip, slip and turn shape, we need to balance on our edges and control their angles.
that explained why we need higher edge angle on steep terrain!