Open readings address the larger aspects of your life rather than a specific problem area or question. They're usually done when you're entering a new phase of life, such as getting married, graduating from college or starting a family. You can somewhat direct the reading if you have a general area you want to cover, such as your career or health, but that's as specific as the direction gets.
The first documented tarot packs were recorded between 1440 and 1450 in Milan, Ferrara, Florence and Bologna when additional trump cards with allegorical illustrations were added to the common four-suit pack. These new decks were called carte da trionfi, triumph cards, and the additional cards known simply as trionfi, which became "trumps" in English. The earliest documentation of trionfi is found in a written statement in the court records of Florence, in 1440, regarding the transfer of two decks to Sigismondo Pandolfo Malatesta.