What is the backstop and when will it be 'reviewed'?
What is the backstop and when will it apply? The 'Irish backstop' was originally designed as a way of keeping Northern Ireland's regulations for trade closely aligned to the EU in order to preserve an open Border.
However, in recent weeks it has evolved into a 'UK-wide customs arrangement' whereby all of the UK would stay in a customs arrangement for a period of time.
The details of this still have to be resolved, including what happens in Northern Ireland if the rest of the UK wants to leave the arrangement.
What is the Review that the Taoiseach is open to?
UK Prime Minister Theresa May wants to be able to assure MPs that there will be a way out of the customs arrangement. The 'review' will be presented as this exit clause.
Surely the backstop is useless if the UK can simply call a review and leave?
The Irish Government insists that Northern Ireland will only be allowed to leave the EU customs network if both the EU and the UK agree to this. The official line is that Northern Ireland will remain inside "unless and until" a better way of ensuring a soft Border is found.
What is Theresa May's next move?
If a deal is agreed, Mrs May must arrange a debate in the UK Parliament. This will culminate in a vote to determine whether it is supported by a majority of MPs. This will be the moment of truth.
Who gets to vote?
There are 650 elected MPs who sit in Britain's House of Commons. The vote is decided by a simple majority.
How will the parties vote?
Theresa May's Conservative Party has 315 MPs.
It governs with a working majority of 13 thanks to a deal with the 10 DUP members. But her party will not be united behind her plan. Eurosceptics think that it leaves Britain too tied to EU rules.
And the pro-EU side says that the ties are not close enough. Both groups are potentially large enough to inflict defeat. The support of the 10 DUP members is dependent on the solution agreed on the Irish Border.
The opposition Labour Party has 257 MPs. Led by Jeremy Corbyn, the party has pledged to vote down any deal that does not meet its criteria. The plans currently under discussion are unlikely to do this.
So most Labour lawmakers can be expected to vote against Mrs May.
However, some who disagree with Mr Corbyn's stance could rebel and vote with the government in order to avoid the risk of leaving without a deal.
What if Mrs May loses?
This would be a politically explosive outcome that could topple her government.
There are legislative guidelines on what happens next, but they could be overtaken by events.
By law, if the government motion is rejected, ministers have 21 days to set out in a statement how they intend to proceed.