Three approaches to not selling people rubbish, and they are genuinely different — one checks at the end, one builds it in as you go, one makes it a culture.
Quality control (QC) — inspect the finished output and reject what fails. Simple, and it finds faults after you have already paid to make them.
Quality assurance (QA) — build checks into every stage so faults are caught where they happen. Prevention rather than detection. Standards such as ISO 9001 sit here.
Total quality management (TQM) — quality as everyone's responsibility, continuously, with the internal 'customer' being whoever receives your work next. Associated with kaizen, continuous small improvement, and with the idea of getting it right first time.
Poor quality costs money in three places: waste and rework, warranty and returns, and lost customers. The last is the largest and the only one that never appears in the accounts, which is why quality is chronically under-invested in.
Distinguish clearly between control and assurance — detection versus prevention — then apply it to the business's actual problem.