The VIEW_DEFINITION column has most of what you see in the Create Table field that SHOW CREATE VIEW produces. Skip the words before SELECT and skip the words WITH CHECK OPTION. Suppose that the original statement was:

CREATE VIEW v AS
  SELECT s2,s1 FROM t
  WHERE s1 > 5
  ORDER BY s1
  WITH CHECK OPTION;

Then the view definition looks like this:

SELECT s2,s1 FROM t WHERE s1 > 5 ORDER BY s1

The CHECK_OPTION column always has a value of NONE.

MySQL sets a flag, called the view updatability flag, at CREATE VIEW time. The flag is set to YES (true) if UPDATE and DELETE (and similar operations) are legal for the view. Otherwise, the flag is set to NO (false). The IS_UPDATABLE column in the VIEWS table displays the status of this flag. It means that the server always knows whether a view is updatable. If the view is not updatable, statements such UPDATE, DELETE, and INSERT are illegal and will be rejected. (Note that even if a view is updatable, it might not be possible to insert into it; for details, refer to Section 19.2, “CREATE VIEW Syntax”.)

The DEFINER and SECURITY_TYPE columns were added in MySQL 5.0.14. DEFINER indicates who defined the view. SECURITY_TYPE has a value of DEFINER or INVOKER.