Holyrood's electoral system can cause many people a headache.

It can all get a bit complicated when additional members, the D'Hondt divisional methods and different coloured ballot papers enter the conversation.

In the end though, it is pretty simple. We promise.

Voters get two ballot papers - one peach and one purple.

The purple one - or if you want to be fancy, the lilac one - elects your local constituency MSP. In this contest the candidate with the most votes wins just like at a Westminster election.

Stay with us as it is going to get a little bit technical.

So after you have voted for your constituency MSP it is time to cast your vote on the peach regional list. There will be a list of parties to choose from and you vote for one and one only.

If you want to vote for a different party on the regional list than the one you voted for on the constituency then you are free to do so. You can also stick with the same one and vote for that party twice.

The additional or regional MSPs are allocated to parties through a system of proportional voting.

Again, though, it's not quite that simple. This is where the D'Hondt method comes in, which has been known to leave people tearing their hair out.

This formula allocates each party additional members by adding up their regional votes and then dividing them by the number of constituency seats each party has won in that region plus one.

After the votes have been divided in this way, the party with the most votes claims the first additional member seat.

This "divisor" is increased by one for each party which gains an additional member, and the calculation is repeated until all the additional seats in the region are filled.

Or to put it simply, the better a party performs in the constituency vote, the more difficult it becomes to win regional list seats.

The purpose of the D'Hondt method is help "compensate" smaller parties who would normally lose out in a First Past The Post election, and to create a parliament more representative of how people voted.

But there's no need to bash your head off the desk running all the calculations -- unless you like doing that sort of thing.

In the end, it comes down to two votes: one for your constituency MSP, and one to pick your party of choice in your region.