Third party logistics (3PL) providers handle specific parts of the supply chain like transportation and warehousing, while fourth party logistics (4PL) providers integrate resources to manage the entire supply chain end-to-end; 3PLs focus on individual functions whereas 4PLs provide complete supply chain solutions and can also manage 3PLs. Key differences include 3PLs handling parts of the process and 4PLs managing the whole process, as well as 3PL services being suited for companies with an existing supply chain and 4PL services being for those seeking an outsourced solution.