An LED Filament light bulb is an electric light bulb which produces light with a LED that is shaped as a filament. Compared to other LED lights, LED Filament lights are omni-directional and have look similar to old fashioned light bulbs.
So how exactly those bulbs are built? Hackaday article [Mike] Illuminates us on LED Filaments gives some details. It notes that LED the strips used inside those bulbs are available in bulk from ebay and Alibaba. Typically entire strip runs best at around 75V and 10~15 mA, while putting out about 1 Watt of light. Mike expermented with those LED strips and posted the results on his [mikeselectricstuff] YouTube channel. He also added the information to his website.