When a single insert, delete or update statement is executed within PL/SQL program then oracle creates an implicit cursor for the same, executes the statement, and closes the cursor. You can check the result of execution using SQL%ROWCOUNT function.
Explicit cursors are created programmatically. The cursor type variable is declared and associated with SQL query. The program then opens a cursor, fetches column information into variables or record type variable, and closes cursor after all records are fetched. To check whether cursor is open or not use function SQL%ISOPEN and to check whether there are any records to be fetched from the cursor use function SQL%FOUND.