Ease of use

Patterns are graded on ease of use

Beginner - no real sewing knowledge required apart from sewing in a straight line. Good patterns to learn to sew with.
Novice -  some knowledge required, like knit cuffs and neckholes
Intermediate - requires a sound knowledge of basics and some knowledge of advanced methods such as gathering, zips and buttonholes
Advanced - more difficult construction methods including set in sleeves, darts, linings and pleats