Henry VI and Edward IV were both kings during the period, both kings of the rival houses, Lancaster and York.
During a battle, Edward IV defeats Henry VI and is crowned king.
King Edward IV lead for around 12 years successfully, but dies in 1438. The right to be king would've been given to one of his two sons, until Richard III locked them in a tower and murdered the two.
Although it's unknown exactly what happened in the tower, there is enough evidence pointing toward Richard III being guilty of murder of the two princes.
The Tower of London is where the two had died, the tower was used for many things, including a prison
The Battle of Bosworth Field was the battle fought between Richard III and Henry Tudor. This is also the battle where Richard, now king, died.
Henry Tudor had a more successful reign than Richard, who had beheaded many who opposed him, and tended to be very oppressive against his own people.
The House of Tudor was the union between Lancaster an York, and was led by Henry VII.