A fuel tax is an excise tax imposed on the sale of fuel. An excise tax, on the other hand, are taxes paid when specific goods are bought, examples are alcohol, cigarettes, gasoline, and gambling etc. Fuel taxes are often considered to be regressive taxes.
What does the government do with these funds?
What each countries government do with fuel tax differ from one another, for example, federal gas tax in America goes into the Highway Trust Fund, the funds generatd are then used to finance most federal government spending for highways and mass transit.
In Canada, a Gas Tax Fund (GTF) was launched in 2015, the aim was to provide a portion of fuel tax to provinces and territories for infrastructural development.