Can someone tell me differences between datareader and dataset

DataReader

1. The ADO.NET DataReader is used to retrieve read-only (cannot update data back to a datasource) and forward-only (cannot read backward/random) data from a database.
2. Using of a DataReader increases application performance and reduces system overheads. This is due to one row at a time is stored in memory.
   //opening connection is must    
   conn.open();    
   string SQLquery = "SELECT CustomerID, CompanyName FROM dbo.Customers";    
   SqlCommand cmd = new SqlCommand(SQLquery, conn);    
   // Call ExecuteReader to return a DataReader    
   SqlDataReader myReader = cmd.ExecuteReader();    
   //The Read method of the DataReader object is used to obtain a row from the results of the executed query.     
   while(myReader.Read())    
   {    
       Console.WriteLine("\t{0}\t{1}", myReader.GetInt32(0), myReader.GetString(1));    
   }    
   //Once you're done with the data reader, call the Close method to close a data reader:    
   myReader.Close();    
   //close the connection    
   conn.close();    

DataSet

1. The DataSet is a in-memory representation of data.
2. It can be used with multiple data sources. That is A single DataSet can hold the data from different data sources holdng data from different databases/tables.
3. The DataSet represents a complete set of data including related tables, constraints, and relationships among the tables.
   string SQLquery = "SELECT CustomerID, CompanyName FROM dbo.Customers";    
   // create DataSet that will hold your Tables/data    
   DataSet ds = new DataSet("CustomerDataSet");    
   //Create SqlDataAdapter which acts as bridge to put the data in DataSet,(data is table available by executing your SQL query)    
   SqlDataAdapter myAdapter = new SqlDataAdapter(SQLquery, conn);    
   //fill the dataset with the data by some name say "CustomersTable"    
   myAdapter.Fill(ds,"CustomersTable");