Composite veneers are made from tooth-coloured resin, and can be directly applied on to the teeth on your first visit itself. After matching the resin shade to that of your natural teeth, the dentist will add the material to your teeth, and follow this up with curing and polishing for a more natural look, all in one visit.
In comparison, porcelain veneers require a minimum of two visits. The first visit usually focusses on taking dental impressions for preparing your custom veneers, and preparing the tooth for the same. The second visit is when the actual veneers are bonded on to the teeth. In the interim period, you might be provided temporary veneers as needed. GlamSmile veneers require minimal to no tooth prep, and are preferred over traditional veneers for more reasons than one.
Another important point to note here would be that composite veneers can be reversible; however, traditional porcelain veneers are not. Most GlamSmile cases can be reversed as no/very little tooth structure is removed.