Different types of cursors:

Implicit cursors:

• These cursors are invoked implicitly.
• User need not create, open, fetch or close the cursor.

Explicit cursors:

• These cursors are not invoked implicitly.
• User needs to create, open, fetch or close the cursor.

Static Cursor:

• Stores a complete copy of the result set.
• Used mostly where scrolling is required.
• Static cursors don’t support updates.

Forward - only cursors:

• This cursor supports updates but not scrolling.
• It supports only fetching serially.
• Rows are not retrieved from the database until they are fetched. 

Forward - only cursors / Read only cursor:

• These are the fastest of the cursors and cannot be updated.
• They cannot be created on query that returns only read only columns.

Key set driven:

• It is a scrollable cursor that cannot be updated. These cursors are controlled  by a set of physical identifiers called as key set. 
• The keyset is built in a  temporary table when the cursor is opened.