All these answers above are mostly incorrect.
Because this plane is massive, it is very heavy. Imagine turning a cruiseliner with a kyack paddle. This is what it would be like for only one aileron. They’ve split the aileron into three separate pieces to reduce work on the hydraulic and electrical systems, as well as reducing stress on the wings and airframe. With these ailerons being near the wingtip, the can also flex the wing to change direction. The ailerons are sometimes at an angle during cruise to reduce wing loading. This is controlled by the FBW system. Airbus has experimented with something like this before, in the A310. The A310 used spoilers instead of airlerons to roll, but was inefficient because of increased drag. Here’s an answer I found on the web:
On a large aircraft, at high speeds the material of the aileron can be flexed so much as to nullify or even reverse the direction of change of lift, which causes significant issues. The further out on the wing an aileron is, the more it is subject to these forces. For high-speed aircraft, this necessitates an outboard/inboard aileron, with the outboard being locked out at a certain speed limit. On the Airbus A380, the downwards motion of the outward aileron is locked out at 240 KIAS, and upward motion at 300 KIAS.
Hope this helps expand you knowledge of aviation!