The State Opening of Parliament is a highly ceremonial event in the British Parliamentary calendar. It happens a number of times each year, at the start of each session, and also shortly after a General Election.
First, a Whip from the Government travels to Buckingham Palace and is held hostage there until the Queen's return. This dates back to when Parliament and the Monarch weren't on good terms!
The Queen travels to the Palace of Westminster in the Irish State Coach. As she passes under the arch into the Palace, a flagman on the roof immediately lowers the Union Flag and raises the Royal Standard. This is because the Palace is a Royal Palace, and hence flies the Queen's standard whenever she is present in it.
She then proceeds to her robing room and processes to the House of Lords. As she goes into the chamber, the lights are turned up to enhance the spectacle of the Royal entrance.
Once she is settled, she sends Black Rod to summon the members of the House of Commons. This is a ceremonial position, so called because he carries a black staff! He arrives at the doors of the House of Commons, at which point they are slammed shut in his face. This is to show the independence of the House of Commons from the Crown. He then bangs his rod (!) on the door, and the members of the house open it. He politely summons them to the House of Lords.
All the MPs then walk slowly to the House of Lords, led by the Prime Minister and the Leader of the Opposition, and crowd by the doors of the House of Lords. Once they are all there, the Queen begins her speech.
The speech beings "My Lords, and members of the House of Commons..." and goes on to say what "My Government" intends to do during the period of sitting. However, the speech is actually written by the government anyway!
Once the speech is finished, the Members of the House of Commons return to their chamber, and the debates start. But again, to show independence from the Crown, they make a ceremonial point of discussing something totally unrelated first. Traditionally, this is the "Outlawries Bill". Its official short title is "A Bill for the more effectual preventing clandestine Outlawries". This dates back to 1676 and is never actually printed or presented by any member.
After this, the Prime Minister makes an initial speech in the debate over the Queen's Speech, followed by the Leader of the Opposition and the leaders of the other parties. And business returns to normal.