OracleDataAdapter.fill()方法是干什么的？有什么作用

 public DataSet SelectDataSet()
    {
        using (OracleConnection connection = new OracleConnection(connectionString))
        {
            DataSet ds = new DataSet();
            try
            {
                connection.Open();
                
                OracleDataAdapter dbDataAdapter = new OracleDataAdapter(dbSelCommandString, connection);
          
                dbDataAdapter.Fill(ds);
            }
            catch (System.Data.OracleClient.OracleException ex)
            {
                throw new Exception(ex.Message);
            }
            return ds;
        }