SkyTeam Elite passengers enjoy benefits such as:

• Priority reservation wait list (when fares permit)
• Preferred seating
• Priority check-in counters
• Priority boarding or at leisure
• Extra baggage allowance

The Elite Plus-status level receives the above, as well as:

• Guaranteed full-fare Y-class reservation on sold-out long-haul flights, at least 24 hours prior to departure.
• Access to airport lounges worldwide, whatever the class of travel, for members in possession of a boarding pass, accompanied by a guest.
• Priority baggage handling on arrival, whatever the class of travel
• Extra baggage allowance

Taken from: https://www.skyteam.com/en/about/faq/elite-elite-plus