Dataset specifies a reference to the data store described by the linked service. When we put data to the dataset from a SQL Server instance, the dataset indicates the table's name that contains the target data or the query that returns data from different tables.
Linked service specifies a description of the connection string used to connect to the data stores. For example, when we put data in a linked service from a SQL Server instance, the linked service contains the name for the SQL Server instance and the credentials used to connect to that instance.