A ‘pill’ or more commonly known as a bobble, fuzz ball, or lint ball is a small ball of fibres that form on the face of a piece of fabric. It is caused by abrasion between two surfaces. Loose fibres have a natural tendency to move to the surface of a piece of fabric, where they are subject to friction, this causes the fibres to twist together into small balls
Pilling is more noticeable on synthetic fibres. This is mainly because natural fabrics shed loose fibres easily and less noticeably, while man-made fibres are extremely strong, so the pills are anchored strongly to the fabric.
Transfer pilling is when the pilling is a different colour to the main base fabric. This occurs when two fabrics have pilled together. Clothing, throw rugs or cushions are normally the cause.
As pilling is not a fabric defect or fault it is not covered under warranty.
For more information on pilling please read this article: Understanding fabric pilling