It appears that the word citation and references are use interchangeably. Are they the same thing?
IEEE uses a style that is common for journal articles and academic works. The citation is the full "description" of the work -- author, title, date, publication, etc. The document you linked describes the citation styles for various kinds of works and calls them "citiation standards".
The reference is the in-text pointer to a citation. While a citation might be:
 Bovik, H. Q., "Parallel Languages for Parallel Universes," Otherworldly Computing, 3(391-407),1990.
The reference would look something like:
On the other hand, Bovik  asserts that parallel languages have the following properties...
Confusingly, citations are usually listed at the end of the paper in a section called "References", though sometimes you see "Works Cited". If IEEE has guidelines for the title of this section, I couldn't find it.
The answer by Monica Cellio is not quite correct.
The heading for the list of references is "References". The IEEE Editorial Style Manual clearly labels this section with that heading:
As the title of that section indicates, it contains references:
Many of the terms have multiple meanings, both according to IEEE usage and elsewhere:
A source is a document from which you cite.
A citation is
a. the act of quoting text from a source
b. the quotation
c. the act of refering to the source of the quotation
d. the reference
A reference is
a. a mention of a source of information
b. the source
In short, the terms source and reference can be used interchangeably, and the terms citation and reference can be used synonymously, but they can also mean different things.
In IEEE usage, the words "citation" and "reference" sometimes mean the same things, sometimes not.