Two strands crossed to opposite sides, in a downward or upward direction to create a crisscross effect is known as:

The description provided in the question fits the term "overlaps" best because it refers to the action of crossing strands over one another in a specific manner to create a distinct crisscross effect. This technique is significant in hairstyling as it can add dimension and visual interest to a hairstyle. When two strands are crossed to opposite sides in either an upward or downward motion, this creates an overlapping pattern that can be used in various styles such as braids or other structured forms.

Understanding this concept is important in hairstyling because mastering such techniques allows stylists to create unique and fashionable looks that can enhance the overall aesthetic of a hairstyle. Other options like weaving, interlocking, and plaiting refer to different techniques and may not specifically encapsulate the action of crossing strands as described in the question. Each of those techniques has its own definition and application in hairstyling, making "overlaps" the most fitting choice in this instance.