The simple version.
Ramp Fuel
Total fuel on board the aircraft before starting af engines.
Minimum Ramp Fuel
Is the sum of taxi fuel, trip fuel, contengency and final reserve fuel plus, if required, alternate fuel and additional fuel.
Taxi Fuel
A quantity to cover APU consumption, engine start and groundmaneuvers until start of takeoff.
Trip Fuel
Is fuel required from the aerodrome of departure to the destination, based on planned operating conditions.
Contingency Fuel
Is fuel required to cover deviations during flight from the "Planned operating condition" as well as to provide operational flexibility in case off in-flight malfunctions.
Final Reserve Fuel
Is the amount required to fly for 30 min. at holding speed at 1500 ft. above the alternate aerodrome (or destination when no alternate required) under standart condition and estimated weight.
Alternate Fuel
If alternate(s) aerodrome is required, it is the fuel to fly from your destination aerodrome to the alternate(s), based on planned operating conditions.
Additional fuel
1 If planning without destination alternate, fuel must be carried for 15 min. holding at 1500 ft. above destination in ISA conditions.
2 Fuel to cater for a failure of a power unit and/or the pressurization system at any point along the route, making it possible to proceed to an intermediate alternate or destination aerodrome. Hold there for 15 min. at 15oo ft. in IAS conditions, and to make an approach/landing.
As initially stated, this is the simple version, and I wouldn't like to expand further on this topic.