Short answers, pulled from the story.
Ken Kutaragi, the CEO of Sony Computer Entertainment, declared the PlayStation Portable the Walkman of the 21st century. This statement positioned the device as a revolutionary multimedia hub rather than just a game console.
The PlayStation Portable was first unveiled at a press conference on the 11th of May 2004. Development had been announced earlier at E3 2003.
The PlayStation Portable was the only handheld console to use an optical disc format known as the Universal Media Disc or UMD. The UMD drive was eventually discontinued when the last Japanese factory producing them closed in late 2016.
The PSP Go was released on the 1st of October 2009 and lacked a UMD drive. It featured 16 GB of internal flash memory which could be extended by up to 32 GB with a Memory Stick Micro.
Sony shut down access to the PlayStation Store for the PlayStation Portable on the 31st of March 2016. The PlayStation Vita became the successor device which offered backward compatibility with PSP games released on the PlayStation Network.