Below are some terms you might find in my sewing patterns.

Backstitch: Stitching back over the top of existing stitches to prevent the stitches from coming undone.  Unless otherwise indicated, you should backstitch the beginning and end of every seam.  Either use the reverse function on your sewing machine, or pivot 180 degrees and sew back over the last 3-5 stitches.

Baste: Temporary stitching used to hold pieces in place.  Taking the time to baste layers in place will give you better finished results. Increase your stitch length to 3.0+ for machine basting (generally not removed).  If you want/need to remove the basting stitches, hand stitch them using contrasting thread that is easy to see.  

Darts: Fold stitched into the fabric to provide dimension in accessories.  In apparel sewing, darts are generally used for fitting purposes. Darts are sewn directly on the guidelines (i.e. there is no seam allowance).  

Edgestitch (aka: edge stitch): Stitching seam parallel to an edge at either 1/16" or 1/8".  The terms edgestitch & topstitch are sometimes used to mean the same thing.  

Grading: Trimming each layer of the seam allowance to a different width.  This removes bulk and improves the look of seams with multiple layers of fabric.  

Interfacing: A material used between layers of fabric to stabilize and firm up the fabric.  There are both fusible and non-fusible interfacings.  Most accessories use fusible interfacing.  My favorite interfacing is HTC Form Flex All Purpose woven cotton interfacing.  If it isn't available I look for Pellon SF101 (sometimes called "Stacey"). 

Interlining: A reinforcement/padding layer typically used on the wrong side of the lining layer. Unlike interfacing, interlining is not a specific product and a variety of materials can be used as interling: flannel, fleece, batting, canvas, scrap fabric, recycled fabrics.

Seam Allowance: The distance between the cut edge of the fabric and the machine needle.

Topstitch (aka: top stitch): Stitching sewn parallel to a seam from the top (right) side of the fabric.  It can be decorative, but also strengthens seams, helps stabilize fabric layers, and adds a finished and professional look to sewn items.  My formula for nice looking topstitching is: long stitch (2.8 -3) + topstitching machine needle (available at the fabric store with the other machine needles) + practice.  The terms topstitch & edgestitch are sometimes used to mean the same thing.  

Quilting Cotton: Medium weight cotton fabric designed for quilting.  It is usually printed,  and tends to be slightly heavier than cotton used in apparel sewing and has less drape.  Large fabric stores often have a section called "quilting cotton", and of course, if you visit a quilt shop, quilting cottons are the prints you see on the racks.  

Pintuck: Small folds of fabric stitched along the edges to provide texture and visual interest.  

Piping: Fabric covered cord used as a decorative edge and to provide structure to seams.

Press: Pressing is done with an iron, but is different from "ironing" in that you aren't moving the iron back and forth across the fabric surface.  When you "press", pick up the iron and move it to the next area of fabric and place it down.

And finally...a common word a number of people have asked me about, so I'll include it here: neaten.  Neaten means to make neat, or tidy.