Fuerteventura is all about surfing. You won't find an inhabitor of the island (who are called 'Majerero's') that doesn't surf, windsurf of kitesurfs. Everybody has a dangerous level of stoke. The islands' name already says it: "fuerte" translates to "strong" and "ventura" to "wind".

The different spots of the island also have to be explained. So here it goes.

Flag beach: easy spot, cross shore, nice swell, can be crowded, huge beach.
El Cotillo: advanced spot, cross shore onto huge stone walls, huge incoming walls of waves which have to be crossed to kitesurf, not crowded - but don't go out alone!
Faro de Tóston: intermediate spot, on shore, beach/reef break, can be crowded
El Buro: lays 5 minute drive south of flag beach, intermediate spot due to more swell, cross shore, not so crowded, more constant winds than flag beach.
Sotavento: probaly the most popular spot everybody knows, when the wind is 14 knts up north it can blow 25 knts at this spot, cross offshore with rescue services, flat waters and a lagoon (check tides), awesome spot to go to when the wind up north is down.
La Pared: located near Sotavento, absolute advanced spot with big swell, reef break, don't go in alone, amazing beautifull spot.
Puerto Lajas: intermediate spot, cross onshore, crowded under locals, nice swell for kickers.