The Government is the institution that runs the country. It is also known as the Executive. The Government formulates policy and introduces legislation in Parliament. Members of the Government are usually either Members of the House of Commons or House of Lords. It is made up of the different departments run by ministers and is headed by the Prime Minister. The Government is formed by the party that gains the most seats in the House of Commons at a general election. The leader of that party becomes the Prime Minister and the Prime Minister selects the Members of the Government from MPs, Lords and very occasionally senior people outside Parliament. The Government does not make laws, Parliament makes laws. The Government can propose new laws in the form of Bills which it presents to Parliament for consideration. In practice, because the Government is formed from the largest party, the laws that it proposes are usually agreed by Parliament.
Further information on this subject can be found from the following links.
About Parliament: Parliament and government
Her Majesty's Government: List of Departments of State and Ministers
Related glossary term: Opposition