A more accurate answer should be posted here.
Needlepoint is always done on a heavy canvas, usually wool thread is used, and the needlepoint stitches cover the entire canvas. The pattern is pre-printed on the canvas. This is often used for upholstery.
Cross-stitch is done on very fine linen with very tiny stitches, usually fine cotton floss is used for the thread, and rarely covers the entire fabric. Cross-stitch is very delicate, whereas needlepoint is very durable. More intricate embroidery stitches as well as beads can be added to a cross-stitch piece. The pattern can be either pre-printed on the fabric or read from a separate paper while working on blank fabric.
I encourage you to read books about cross-stitch and needlepoint for more interesting history and description of this beloved art that dates from ancient times.