what is the apple pencil compatible with?

No, there is no Apple pencil that is compatible with the Air 2.

Here is the definitive compatibility list for Apple Pencil:

Apple Pencil (2nd generation)

You can use Apple Pencil (2nd generation) with these iPad models: 

• iPad Pro 12.9-inch (3rd generation) and later
• iPad Pro 11-inch (1st generation) and later

Apple Pencil (1st generation)

You can use Apple Pencil (1st generation) with these iPad models:

• iPad Pro 12.9-inch (1st or 2nd generation)
• iPad Pro 10.5-inch
• iPad Pro 9.7-inch
• iPad Air (3rd generation)
• iPad (7th generation)
• iPad (6th generation)
• iPad mini (5th generation)

Apple Pencil compatibility - Apple Support

Not sure which iPad you have? Identify your iPad model.

See: Select Apple Pencil - Apple