Line Support

The definition tends to vary from company, sector etc :

1st Line Support – Helpdesk (Job titles such as Helpdesk Analyst, First Line Support, Call Logger)
Typically involves resolving calls over the phone in a service desk environment and may escalate to 2nd line support.

2nd Line Support – Desktop Support (Job titles such as IT Technician, PC Engineer, Desktop Support Analyst)
Typically involves onsite desktop support of all workstations, printers, scanners etc

3rd Line Support – Network Support (Job titles such as Network Admin, Network Manager, Server Engineer)

Typically involves onsite support of all servers and dedicated to maintenance of network related issues.