The FCE is the test of competence in English. Once a student has passed this exam, that student can honestly say "I speak English". This does not mean that the student is a fluent English speaker, but it does mean that if this student operates in an English-language environment, he or she will probably go on to become fluent.
As it is, the students are expected to be able to understand most of the English they encounter, though sometimes this may take much more work than it would take an experienced user. (For example, it may take several readings and the use of a dictionary to read a newspaper article.)
A person with the FCE might be expected to work in an English-speaking environment as a business person or student. This person will be able to understand public announcements, and also hold converations in English.
For example, people with the FCE will be expected to read texts and understand particular details as well as what the whole text is about. They will then be expected to be able to produce a summary of the report, or to decide which parts are wrong or right. These reports may be delivered as speech or text.