"Preferred seats" are just more legroom than regular economy, and a little more comfortable seat.

Economy Plus - these seats have more legroom (same as preferred seating), and you also get a free meal and drinks if seated there.

There are 2 ways to get a seat in Economy plus - Either you buy an economy plus ticket, which normally costs alot more, (and includes free suitcase and earns more points), Or you buy a regular ticket and then pay $60 to sit in Economy plus. (If you have an Elal Flycard, you get these free if available at check-in).