Some knitting terms and their meanings are "cast on" and "bind off" that refer to starting and finishing a knitted piece, "rep" or "repeat" that means to repeat the pattern and "tog" or "together" that implies to work several stitches together. "Increase" and "decrease" refer to adding or removing stitches.
Various knitting terms are used in the instructions of a knitting pattern to make it easier for comprehending the directions and to save space. "K" refers to knit stitch and "P" means purl stitches. "Cast on" is abbreviated as CO and "bind off" is abbreviated as BO. BO is sometimes also referred to as casting off or finishing the knitted item.
To increase stitches when knitting, work the same stitch on the front and back for both knit and purl stitches. To decrease stitches, work two or more stitches together. Increasing and decreasing can be done in other ways too as per the specific instructions given in the pattern.
"Work even" implies continuing the pattern without making any increases or decreases. "Yarn over" or "YO" refers to taking the yarn over the knitting needle and "slip" means to simply slip a stitch from one needle to the other. "Maintain pattern as established" implies to retain the center portion of the pattern as is and to add or remove the required number of stitches at the ends without affecting the pattern. RS refers to right side and WS refers to wrong side.