A Europhile is a term for a person who wants to reduce government on the level of the nation-state and increase centralised government by the European Union: they believe the benefits of further sharing sovereignty outweigh the disadvantages. The term is often used in a pejorative sense but this isn't always the case.
A major argument of Europhiles is the relative small size and importance of the individual European countries with respect to the current and rising powers on the world scale. Countries such as France, the United Kingdom or Germany, once major powers, have now been overtaken by the United States and will be made even less relevant with the increased importance of countries such as China and India.
The individual countries, they argue, would then have limited geopolitical influence and would be unable to represent their own interests effectively. On the other hand, a united Europe, with a population and an economy larger than that of the United States, would make a viable partner, or competitor, whose opinion and interests would be taken into account on the world stage. An example often advocated is trade agreements and disputes, where the EU's negotiations on behalf of its constituents may produce better terms than would be possible separately .
An integrated single market, with common regulations, is also potentially more attractive for external investment, providing greater economies of scale and liquidity.
In the British context, Europhiles tend to be in favour of British adoption of the Euro.
Europhile vs. Pro-European
From its etymology, "Europhile", which could just define the sentiment of belonging to a community of people, is mostly used to infer connotations of unconditional or irrational 'love' of integration, that would indicate dogmatic support for integrationist policy irrespective of the potential negative consequences.
As such, some consider the term innaccurate when applied to EU support that's based on a cost-benefit view that weighs practical benefits versus loss of national sovereignty. Due to this, the term pro-European is most often used by pro-EU political parties and other organisations.
The difference is akin to that between euroscepticism (rational questioning of policy) and europhobia (an irrational fear of such ideas).