A long dc is a variation of a normal double crochet.
While a double crochet has a specific height which is the same throughout a project, it is the special characteristic of a long double crochet that it is elongated in order to cover the distance between the front loop / stitch it is worked into and the current row.
The long dc is preferable over a treble, double treble or triple treble, when a less ‘twisted’ stitch structure is required than those stitches provide.
In comparison with these long stitches, the long dc is wider, looser and slighter more elastic.
Due to the twisting from working through the several yarn overs, standard long stitches have a very regular, repetitive structure. The long dc_Star maintains the same form and the typical features of the double crochet, no matter how long it is stretched.