The "Textus Receptus" or "Received Text" was the first Greek version of the New Testament printed using the printing press. For many centuries the Roman Catholic church preferred a Latin version of the New Testament as they considered Latin to be superior to Greek. One legendary story describes how the church sold a large amount of very early Greek copies of the New Testament to a Chinese businessman as he considered the papyrus to make excellent fireworks wrappers.
As the original copies of the New Testament were written in Greek, they came under certain pressure to produce an authorised version of the Greek NT. Desiderius Erasmus was commissioned by the church to produce it and he completed it 1516. Because of the urgency placed on this task by the church, he only managed to find a handful of very late Greek manuscripts to work with. In addition these manuscripts were in such a dire state that he did not have a complete version of the book of Revelation and had to translate parts of the book from a Latin manuscript. In comparison, modern translators have thousands of copies of the NT and many of them are centuries older than the copies used by Erasmus.
The Textus Receptus is generally considered to be an extremely poor version of the Greek New Testament because of the use of these late copies which contained various mistakes and additions by made later copiers. What makes this frightening is that the King James Version of the Bible, which for a long time was considered to be the authoritative version of the English Bible, was solely based on the Textus Receptus.