THE SNP have confirmed they will be backing the Common Market 2.0, or Norway Plus, model during tonight's indicative votes - but what does it mean?

The MPs in favour claim that it would return the UK's relationship with the EU to something that resemebles what the UK had with the European Economic Community in the 1970s and 80s, while keeping the UK outside closer political union and the European Court of Justice.

It would also involve keeping freedom of movement, as well as requiring paying money in to the EU and following some EU regulations without much say in how they are shaped.

The Common Market 2.0 proposal is essentially to leave the EU, but keep the UK within the European Free Trade Association (EFTA) but with some changes.

So how does it work?

There are currently 28 EU countries and three non-EU nations that comprise of the European Economic Area (EEA). These non-EU nations are Norway, Iceland and Lichtenstein, and they are part of the single market but NOT the Customs Union.

They are also all part of the European Free Trade Association, along with Switzerland which is not part of of the EEA.

Membership of EFTA means freedom to set policies outside of the EU's Common Agricultural Policy (CAP) and the Common Fisheries Policy (CFP), as well as being exempt from EU rules on justice and home affairs.

EFTA countries all pay in to the EU, and still follow many EU rules.

As EFTA members are not members of the EU Customs Union, they are free to sign their own trade deals with other countries, and will be subject to some custom checks on goods moving between EFTA and EU countries.

What about Northern Ireland?

To prevent a hard border between Northern Ireland and the Republic of Ireland, some MPs are proposing an arrangement that essentially mirrors a Customs Union - and this is where the "Plus" of Norway Plus comes from.

One major problem with this is that this solution currently breaks the EFTA's rules.

What else?

Whenever the EU passes any legislation relating to the Single Market, then Norway, Iceland and Liechtenstein also need to bring it into their domestic law.

The UK would effectively have some policies set without the ability to vote on them, though it would still be possible to have influence on any potential outcome by sitting on committees at the early stages of new proposals.

They can also challenge legislation through the EEA Joint Committee, which includes the EU and all EEA members.

Finally, how much would it cost?

Being a member of the EFTA, the UK would likely pay a lot less into the EU than it does at the moment.

How much was paid in would depend on which EU programmes the UK chooses to be involved with.

Some have suggested that it would be between two thirds and 88% of current expenditure.