L1 customer support resolves the preliminary level issues arising in a product or service, such as installation, reinstallation, and uninstallation. They create customer tickets if a deeper resolution is required.
L2 customer support works on the tickets raised by L1 support to resolve complex issues with their knowledge and expertise about the product or service.
L3 customer support comprises the development team that handles technical issues and are adept at performance tuning and bug fixing.