This is a S'well bottle.

If you're not familiar with S'well bottles, they are highly designed, fairly well constructed vaccum insulated water bottles.  They're quite popular and you see them everywhere - at the office, in the gym, in classrooms, pretty much anyway you go.  The bottle's vacuum insulated construction allows beverages to remain cold for 24 hours and hot for 12 hours.

[source: swellbottle.com]

Comparing a Passive House to a conventionally built house is like comparing a S'well bottle to a regular water bottle. If you want to naturally maintain the temperature in a container whether it's as small as a bottle or as big as house you need to apply the same two core principles - namely they need to be air-tight and wrapped in heavy insulation. Imagine the S'well bottle with the cap off, despite having a well insulated bottle, your cold water quickly comes to room temperature on a hot summer day - that's why you need to employ both principles to make it work.

Also, here's a popular video from Hans-Jörn Eich which explains the basics and benefits of passive house design in 90 seconds. Including it is simply a must for any respectable passive house blog.