There are hundreds of different kinds of knitting stitches, but the two basic building blocks of the majority of these stitches are the knit stitch and the purl stitch. Almost all other knitting stitches depend on these two stitches to make patterns and textures, although other techniques, such as placing stitches on a holding needle or dropping stitches, are used as well. Most of these more advanced stitches can be used both on circular needles and straight needles, but often require the stitches to be in a specific multiples so that the pattern repeats completely.
Several techniques exist for making knit and purl stitches. These techniques all end up with the same ending and mainly differ on which hand holds which needle. Most people have difficulty following written instructions detailing how to make these knitting stitches, but the process is really quite simple when viewed. A video or diagram is therefore often the best way to learn how to knit and purl. While there are differing techniques for making these basic stitches, the exact pattern for making more complicated stitches cannot be modified, as where the basic stitches sit in relation to each other is what creates the pattern.
A knit stitch passes through the stitch it connects to vertically from below. A purl stitch is the opposite and connects from above. These are exact opposites of one another, and what is viewed as a knit stitch on one side of the fabric will appear as a purl stitch on the other.
These two building blocks can be combined in patterns to make different knitting stitches. One of the simplest stitches is called the garter stitch, which consists of only knit stitches, or only purl stitches, on both sides of the fabric. Stockinette stitch uses alternating rows of all knit and all purl stitches. Ribbed stitches consist of alternating between knit and purl stitches on the same row, and then reversing the pattern on the other side such that stitches that were knit are now purled, and stitched that were purled are now knit.
More complicated knitting stitches can be made that produce specific textures and images. Seed stitch, for instance, has a raised pattern that looks like seeds or moss. Cable stitches raise and move certain sections of knitting, giving a braided appearance to the piece. In shadow knitting, the appearance of stitched is used to create a picture when the piece is viewed from a certain angle.
Knit and purl stitches may not only be placed in specific patterns, they may also be modified. For example, making a stitch that uses more yarn than would normally be used at that gauge is called an elongated stitch. A stitch that is twisted a certain amount is sometimes called a plaited stitch. Other techniques using these stitches change the number of stitches in a row, but still often use basic knit and purl stitches. By creatively decreasing, increasing, dropping, and picking up stitches, a lace pattern can be formed which itself can be thought of as a stitch.
There are many books that contain directions for hundreds of knitting stitches. These small stitch dictionaries typically employ abbreviations and graph diagrams to show how to make the stitch. While these can initially be difficult to understand, the abbreviations are generally fairly standard and become easier to follow with a little practice.