Electricity certificates are a means of promoting electricity produced from renewable sources, like the sun, wind, water. A defined share of all electricity you consume as a customer must be electricity from renewable sources. This is called the customer's quote duty. The electricity trading businesses must report this quote to Energimyndigheten (the Swedish Energy Agency).
An example: A producer with a wind turbine power plant can sell the electricity produced, as well as the electricity certificate and the guarantees of origin. All electricity trading businesses are obliged to buy electricity certificates to cover the quote duty of their customers, and they must report this to the Swedish Energy Agency.