What is the benefit of "using"

I want to understand the difference between

public DataTable ExectNonActQuery(string spname, SqlCommand command)
 {
     using (DataTable dt = new DataTable())
     {
         cmd = command;
         cmd.Connection = GetConnection();
         cmd.CommandText = spname;
         cmd.CommandType = CommandType.StoredProcedure;
         da.SelectCommand = cmd;
         da.Fill(dt);
         return (dt);
     }
 }
 

and

public DataTable ExectNonActQuery(string spname, SqlCommand command)
 {
     DataTable dt = new DataTable();
     cmd = command;
     cmd.Connection = GetConnection();
     cmd.CommandText = spname;
     cmd.CommandType = CommandType.StoredProcedure;
     da.SelectCommand = cmd;
     da.Fill(dt);
     return (dt);
     }
 }
 

I actually want to understand what is the benefit of creating a new object using "using" instead of creating it directly like this

DataTable dt = new DataTable();
 

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