What happens after you file a patent application, in the US and EU?

As soon as you file in the US, your invention is patent pending. This carries no enforceable rights yet, but it puts competitors on notice and lets you use the term publicly, lasting until grant, abandonment, or, for provisionals, the 12 month expiry. In the EU, filing gives you provisional protection rights once the application publishes, functioning similarly in practice and giving certain rights to compensation for infringement occurring after publication, once the patent eventually grants. Both systems publish the application automatically 18 months after the earliest priority date, making it fully public and searchable, including by competitors, regardless of whether a decision has been reached. From there, the US enters the office action queue and the EU enters search and examination.

Sources: USPTO, Patent Process Overview, EPC Article 67, Rights conferred by a European patent application after publication.