Every row in a stream has the same structure, or "schema". The schema comprises the column names, the column data types, and the order in which the columns appear.
For example, in a StockTrades stream, the first column might be a STRING that contains a stock symbol, the second column might be a FLOAT that contains the price per share, and the third column might be an INTEGER that contains the number of shares bought or sold.
Multiple streams may use the same schema. One stream may not use multiple schemas.
The schema defined by the user does not explicitly include the row timestamp, but all rows will have a row timestamp as a "hidden" field.