There are several types of tatted chains.
1. A regularly tatted chain (needle tatting example, all picots are still on the needle.)
2. A chain tatted using the first half stitch only, also called an "S" chain.
3. A chain tatted using the second half stitch only, also called a "Z" chain.
4. A chain tatted with Victorian sets, in this pattern 4 x first half stitch followed by 4 x second half stitch. Also called node stitch, rick rack stitch and zig zag stitch.
5. A chain tatted in the maltese or pearl tatting fashion requiring three threads; no picots on sample.
6. A chain tatted in the maltese or pearl tatting fashion requiring three threads; with picots on sample.
Of these types, the node stitch is particularly decorative. The actual stitch is composed of a series of first half stitches followed by a series of second half stitches. The actual number of the half stitches will vary by pattern. A picot may be placed in the chain as well. The stitches are counted in sets. And then a notation will be given for the number of half stitches in repetition. The directions vary from pattern to pattern but it often looks like: "Tat 3 sets node stitch ( 4 : 4 )."
As the half stitches are tatted a twist or spiral becomes visible in the work. This gives it a ruffled look. It has also been described as looking like rick rack or zig zag. Good tension is needed to have it lay flat when done.
Of course, not all chains are straight lines or curves. Consider this pattern from the Priscilla Yoke Book Crochet & Tatting 1916 pg. 18. Here the node stitch chain is used to create a lattice look in the yoke. It looks a bit complicated at first glance. Although tatted in one straight pass, it is best tatted with 6 shuttles or 3 shuttles and balls. This lattice is very effective when done in two (or more) colors. Using 3 colors you get a very nice repeat.