The Convention aims to increase the effectiveness of jurisdiction clauses and make judgments obtained under those clauses easier to enforce. Currently the Convention applies only as between Mexico and the EU member states (other than Denmark), so the addition of Singapore from 1 October is significant. The US and Ukraine have also signed the Convention but have yet to ratify it.
The Convention may become even more significant to the UK post-Brexit, as the UK can sign up to it without any requirement for agreement from the other contracting states. It is therefore widely seen as a fallback option to avoid any doubts regarding the continued effectiveness of exclusive English jurisdiction clauses and enforcement of English judgments within the EU, in the event that no other agreement or convention is put in place between the UK and the remaining EU member states once the UK leaves the EU.
In broad summary, the Convention provides that where parties have agreed on the exclusive jurisdiction of the courts of a contracting state, this must be respected by the courts of each other contracting state who must (subject to limited exceptions) suspend or dismiss the case if proceedings are brought before them. Contracting states must also recognise and enforce judgments given by another contracting state pursuant to such a jurisdiction clause (again subject to limited exceptions).