third party hdmi to vga adapter does not work

I recently bought an HDMI to VGA adapter and a VGA cable, and when I plug it in it doesn't work properly. I was having problems so I read that the HDMI port on mac does not work, and that you need to use the mini DisplayPort/thunderbolt ports on your mac and that the adapter has to made by apple for it to work properly, is the last statement true? and if it is do apple sell mini DisplayPort to DisplayPort cables or adapters?