There are different types of serrated edges:
Classic serrated edge
It’s the most common type of serrated edge. It has sharp tips that tear through the food, with different “density” of the serration. Usually a less dense serration (less tips and more space in between each tip) has more bite, since the pressure during a cut is distributed on fewer points. A classic serration is preferable when cutting though anything with a harder crust.
In a scalloped edge, the serration is inverted as compared to the classic serration. This makes it less aggressive and the preferred serration when cutting softer food, like cakes or sandwiches, or for carving. It’s not like tearing through food, but more some sort of cutting with an added saw-effect.
Double serrated edge
This edge combines 2 different profiles of serrations. The most common type uses slightly raised, sharp tips, and scallops in between. Such an edge has 2 benefits: it will still be aggressive enough to tear through harder skin or crust of food, but in a much less aggressive way. In effect it’s a combination of tearing and cutting. The 2nd benefit is that the raised tips will protect the scallops from hitting the cutting board, substantially reducing wear and thus making the edge last longer.
Since in most use cases in a kitchen a straight edge produces superior results, it's not surprising that the overwhelming majority of knives sold feature a straight edge, with the most important things you need to know about it explained on the following pages.
Edge Types knifeopedia
There are two types of cutting edges, a straight edge and a serrated edge.
A straight edge, also known as a plain or fine edge, refers to knives that feature a blade with a sharpened cutting side that’s uniform from the heel to tip of the blade. Knives with a serrated edge feature a sharpened cutting edge marked by seemingly jagged “teeth” that extend from heel to tip, like a wood saw.
The biggest advantage of straight edged knives in kitchen use is that they produce a smooth, clean cut, as opposed to serrated knives which actually tear food. However, there are instances where a serrated edge has an “edge”, like cutting food with hard exterior and soft interior, where you need a saw-like cutting motion to cut through a hard crust. In many cases (e.g. tomatoes), such food can also be cut with a sharp knife. But in other cases (e.g. hard crusted bread), it’s recommendable to use a serrated edge, also since a hard crust would wear a fine edge over-proportionally.