This means that the seller contracts for pre-carriage, meaning transportation of the goods from the seller's facility to where they leave the seller's country, and main carriage, meaning transportation from the seller's side to the buyer's side.
This aligns with what the seller is responsible for shipping-wise, but under CPT, although the seller contracts for pre-carriage and main carriage, delivery occurs, meaning responsibility transfers to the buyer, when the goods are turned over to the first carrier.