Translators convert written texts from one language into another.
Translators are not interpreters. Interpreters convert spoken texts. There is, of course, a relationship between these two occupations, but they require very different skills – not in the least different attitudes toward one’s work. Most good translators are not good interpreters, and many good interpreters are at best mediocre translators.
Translators are language professionals. They are applied linguists and
competent writers, diplomats, and lay experts in specific areas. 
Like
linguists, translators have to be capable of discerning subtleties and nuances
in their languages, researching terminology and colloquialisms, and handling new
developments in their languages.
Like writers, translators have to be accustomed
to working long hours alone on a subject which may interest only a few people and with a
language that few people around them know.
Like diplomats, translators have to
be sensitive to the cultural and social differences which exist in their
languages and be capable of addressing these issues when translating.
And
translators have to know the basics and some of the details about the subjects
they deal with.
Translators do not just need to know a foreign language. They also need:
This primarily means the ability to write well in the target language, and the ability to read and understand the source language material very well. This sounds trivial, but it is much more than most people who “merely” speak another language can do. Translators must have a deep interest and dedication to the languages they work with.
This is something that a translator must cultivate. Even the most widely read and broadly educated translators cannot claim to be experts in more than a few fields. So translators specialize: legal, financial, medical, computers, engineering. Translators have to develop – and maintain! – sufficient expertise for the fields for which they are translating material. This does not mean medical translators must be physicians or that computer translators must be programmers. But background experience or education (or both) are essential.
This is necessary for the relationship between translators and their clients to develop smoothly. Translators also need to have mastered the technical aspects of word processing and communications. And in these days of globalization, this means familiarity with business customs in various countries. Translators must regularly invest in the resources necessary to deal with their material: dictionaries, glossaries, databases – and of course personal contacts. Translators work hard to improve their knowledge of the fields they work in by reading related material. In other words, professional translators are always learning.
Translators come from all backgrounds. While a specialized degree in translation is useful, it is far from necessary. Ability counts more than anything else. Most translators are very widely read in their languages, and can write well. Others are fascinated by language and use translation as a way to be close to their favorite subject. Still others are experts in certain fields and use their language skills to work in that field. And in some of the most fascinating and successful translators, all these factors are combined.