If a view is created WITH SCHEMABINDING, the underlying table(s) can't be dropped or modified in such a way that they would break the view. For example, a table column referenced in a view can't be removed.
CREATE VIEW dbo.PersonsView WITH SCHEMABINDING AS SELECT name, address FROM dbo.PERSONS -- database schema must be specified when WITH SCHEMABINDING is present
Views without schema binding can break if their underlying table(s) change or get dropped. Querying a broken view results in an error message. sp_refreshview can be used to ensure existing views without schema binding aren't broken.