Is it a score? ...Is it a crease?... well... it could be either! The truth is, the two terms have been thrown around, mixed up, mashed together and often used to describe the same thing by different people. The actrual reality is that both terms originally meant two totally different processes.
A score is the term given to the process of cutting stock part way through to enable an easy fold. Another common term for this process is "top cutting".
Scoring is often used on thick card, allowing sharp folding for products such as case made boxes. Scoring is also used when folding stock "against the grain", to help create sharp, straight folds. The depth of a score is generally half the thickness of the material that is to be folded.
There are many methods used to achieve a good score, from running the back edge of a knife along a straight edge or ruler... right through to setting a knife height to the nearest 0.01 of a millimetre on a CNC style digital cutter.
CreaseA crease is very different to scoring. Rather than actually "cutting" into the stock, creasing creates a "dent" along the entire length of a desired fold. In order to achieve a good crease, both a male and female "rule" are often needed. The stock is pressed between both to force it to the desired crease shape.
Creases can be done in multiple depths and widths but all have one thing in common, they do not cut into the stock! Rotary creasing is also a method used, the stock is passed through two rollers, the top roller containing a "male" creasing disc, and the bottom roller containing a "female" disc.
Another variation on creasing is the "heat crease" used for Polypropylene Where a heated creasing rule is pressed into the stock to "melt" a crease into the desired profile.