A source document is completed for every transaction as proof of that transaction. The source documents that you learn about at the grade 8 level include duplicate receipt, cash register roll, cash invoices, bank deposit slips, cheque counterfoil and bank statements.
Subsidiary journals are a point of first entry meaning that when a transaction is entered in the accounting records it is first entered into a journal and because there are so many types of transactions and source documents there is also a wide range of journals.