The 'Threshhold updates' are a collection of updates for windows 8.1. Some are saying that this is windows 8.2 but see for yourself:
Reference:
http://winsupersite.com/windows-8/further-changes-coming-windows-threshold
consolidated os
consumer focused
desktop users
enterprise sku
floatingwindows
metro apps
microsoft plans
modernmix
next version
product versions
release information
sku morphing
start menu
threshold
updates
user experience
windows 8.1
windows phone
windows rt
xbox one
