Safety goggles with direct ventilation are goggles that have ventilation holes directly through the frame of the goggles to the inside environment. These ventilation holes are generally very small and placed around the top and/or sides of the goggles. They are excellent for professional and general purpose DIY-ers applications to prevent flying particles from reaching the eyes.
Direct vented goggles are great when there is a large amount of fine debris floating around in the air of the work area. Sure, a pair of safety glasses will protect your eyes from larger debris, but safety goggles add the benefit of forming to your face around the eyes which creates a better seal. So, unless the debris is to come through the very small ventilation holes, the internal environment is safer than when using safety glasses instead of goggles. Direct vent safety goggles are a great choice unless working with chemicals, liquids or extremely fine particle materials.