Under the new system, the examination procedure of a European patent application does not change. Rather, when the European patent is granted, the patent proprietor will have the option to select a Unitary Patent (UP), which will cover multiple states. States that have chosen not to participate in the system can still be covered with national validation of a European patent, under the current arrangements. This will result in a Unitary Patent that covers all of the participating states with a single patent and, if selected, a bundle of national patents in non-participating states.
Use of a unitary patent is not obligatory. It will remain possible to cover any desired selection of states by validating the patent nationally in just those states. You can read more about how you can prepare for the new system here.
UPs will fall within the exclusive competence of a new central patent court: the Unified Patent Court. The new court will hear revocation and infringement cases and will have several local and regional divisions and three central divisions; each one in London, Munich and Paris. You can read more about the Unified Patent Court here.
When the system starts, it will initially cover Austria, Belgium, Bulgaria, Denmark, Estonia, Finland, France, Germany, Italy, Lithuania, Luxembourg, Malta, Netherlands, Portugal, Sweden and the United Kingdom. With time, it is expected that more counties will join, with the notable exception of Spain, which has decided not to participate in the system. Note that the UPC Agreement covers EU states. Therefore, non-EU member states party to the European Patent Convention (the current system) will not be involved in the project. This list includes Switzerland, Norway, Turkey. It remains to be seen how the UK will participate in the system post-Brexit.