MiFID stands for the Markets in Financial Instruments Directive (Directive 2004/39/EC). It has been in force since November 2007, and it governs the provision of investment services in financial instruments by investment firms, and the operation of traditional stock exchanges and alternative trading venues.
In October 2011, the European Commission put forward proposals to revise the Markets in Financial Instruments Directive (MiFID 2). The aim of this was to make financial markets more efficient, resilient and transparent, and to strengthen the protection of investors. (From the European Commission website.)