What is cartel pricing strategies?

It is basically when a set of Companies meet together to fix a price for a product which only they sell in the market. They make a deal with each other to not charge a price lower than the set price. The set price is always or usually over what the product is worth. By doing this they ensure a healthy profit margin and stop other companies from entering the market. This is very hard to proove. Examples would be the Oil Barons in the Middle East or the Oil companies that supply to your petrol station, who can decide their own prices irrespective of outside influences becasuse of the extremely high demands.