Heresy means holding a religious belief which the Church disagrees with;
Treason means trying to overthrow the government.
During this period, religious unity was thought necessary to keep a country together. Religious tolerance was therefore out of the question. Furthermore, the religion of the country depended on the religious views of the monarch. Disagreement with the monarch's religion was inseparable from treason, and many paid the price as England in the 16th century went through a series of religious about-turns.
Henry VIII took the Church in England away from the Roman Catholic Church in the 1530s. Several people who disagreed with this change were executed, including the king's former friend and minister, Sir Thomas More. Under Henry's son, Edward VI, 1547-1553, England became more Protestant, leading to protests and rebellion from Roman Catholics. From 1553 to 1558, England was ruled by Henry's daughter Mary I. She was determined to restore Roman Catholicism. Aided by such supporters as Bishop Bonner of London, (see Source 2) Protestants were arrested, tried as heretics and about 280 of them burnt.
When Elizabeth became queen in 1558 a new, Protestant, religious settlement was made. Elizabeth herself was unwilling to persecute people for their beliefs, and many Roman Catholics continued to worship freely for a while. However, by the 1580s relations between England and Roman Catholic Spain were moving towards open war. The Pope authorised Roman Catholics to rebel against Elizabeth. Her ministers, some of whom, such as Sir Francis Walsingham, were determined Protestants, became worried about the danger to the queen and the country. Roman Catholics were arrested and about 250 were executed, not for heresy, but for treason.
Roman Catholics hoped for greater tolerance from King James when he became king in 1603. When this did not happen a small group of Catholics set out to assassinate him and most of the rulers of the country by blowing up the Houses of Parliament on November 5th, 1605.