There are 3 to 4 tiers / levels of support offered by Support Teams.
Each level having more experience and education in the field of support than its previous level. Some Technical units/organizations/departments have less tiers, but generally there are four. (The L would be for Level.) It could generally apply to any form of technical support.
They are different levels of support provided by companies (Generally technical). Each level is skilled in their job and it increases as you move a level up. Each level having more experience and education. It could generally apply to any form of technical support.
Usually they all are Service Levels
L1 : Product Demo Basic troubleshooting
L2 : Technical Problem
L3 : Major problem
and so on…