Short answers, pulled from the story.
Catherine Howard was the fifth wife of King Henry VIII, serving as Queen of England from July 1540 until November 1541. She was the niece of Thomas Howard, 3rd Duke of Norfolk, who placed her in the household of Henry's fourth wife, Anne of Cleves, where Henry became captivated by her. They married on the 28th of July 1540 at Oatlands Palace in Surrey.
Catherine Howard was about 17 years old when she married Henry VIII, who was 49 at the time. Her exact birth year is uncertain, with historians generally accepting circa 1523 as most likely, though 1522 has also been proposed.
Catherine Howard was executed on the 13th of February 1542 on grounds of treason. She was accused of adultery with her distant cousin Thomas Culpeper and of concealing her earlier sexual relationships with Henry Mannox and Francis Dereham before her marriage to the king. No formal trial was held; a bill of attainder was passed by Parliament on the 7th of February 1542.
Thomas Culpeper and Francis Dereham were arraigned at the Guildhall on the 1st of December 1541 and executed at Tyburn on the 10th of December 1541. Culpeper was beheaded and Dereham was hanged, drawn and quartered. Their heads were placed on spikes on London Bridge, where they remained until 1546.
There is no authenticated contemporary portrait of Catherine Howard. Two miniatures by Hans Holbein the Younger, one in the Royal Collection at Windsor Castle and another in the Buccleuch Collection, have long been associated with her, but both identifications are now disputed. Art historian Franny Moyle argued in her 2021 book The King's Painter that the Windsor miniature more likely depicts Anne of Cleves.
Assessments range widely. Earlier biographers including Lacey Baldwin Smith (1961) and Alison Weir described her in harshly critical terms. More recent scholars such as Conor Byrne, Gareth Russell, and Lucy Worsley have argued she was an exploited child rather than a willing participant in the relationships that led to her downfall. The debate centres on her age, the lack of adult supervision during her adolescence, and the retroactive nature of the law used to convict her.