Prime Minister David Cameron and First Minister Alex Salmond have signed an agreement about the 2014 Scottish independence referendum.
A referendum is a vote where people are asked to either accept or reject a particular proposal.
Scottish people will be asked a single Yes/No question on whether Scotland should leave the United Kingdom.
The deal sets out key details of the vote, which will take place in autumn 2014.
Part of the agreement has been to lower the voting age,v, allowing 16 and 17-year-olds to take part.
The UK government will grant powers for the Scottish Parliament to hold a legal referendum, under a mechanism called Section 30.
Scottish Secretary Michael Moore and Scotland's deputy first minister, Nicola Sturgeon, negotiated the agreement.
The Scottish National Party, led by Alex Salmond, want independence from the UK and complete control over the way the country's run.
The Prime Minister said keeping the United Kingdom together was his number one priority.