When calling tech support, customers usually go through a series of "tiers" or levels of difficulty.
Tier 0 includes various self-service tools like service catalogs, manuals, and the knowledge base a company provides their customers with to help them fix the technical issue themselves.
Tier 1 includes dealing with basic tech support. The agents help customers with basic issues, but if they can't solve your problem, they'll likely escalate it to Tier 2.
Tier 2 is where things start to get more serious. The agents at this level are more knowledgeable, and they have the ability to run diagnostic tests and access your customer’s account information. If they can't solve your problem, they'll escalate it to Tier 3
Tier 3 is the last stop before escalation to a senior engineer or manager. The agents at this level are expert troubleshooters, and they have access to all the tools and resources necessary to resolve even the most complex issues.
Tier 4 includes outside technical support in case the company can’t deal with the issue.