Wholesale prices are the amount retailers pay for buying power from the grid.
Wholesale prices, also know as "spot prices", change every 5 minutes which makes them far more volatile than regular rates. They drop when the grid has lots of stored energy but demand for power is low.
If generation is low but demand is high, prices can skyrocket. Ongoing generation issues with high demand in periods like winter and summer can contribute to worsening the energy crisis.
Unless your provider offers wholesale prices like Energy Locals or Amber Electric, you won't need to worry about them.