What it measures
Quick ratio is current assets minus inventory, divided by current liabilities. The current ratio's close relative, deliberately harder to satisfy: inventory counts as a current asset, but it isn't always close to cash, a warehouse of unsold goods can't necessarily be converted to cash fast enough to cover a bill due next month.
A company can look fine on current ratio and noticeably tighter on quick ratio if a large share of its short-term assets is sitting in inventory rather than cash or receivables.
A worked example
The same company from the current ratio example, 450 million in current assets, 300 million in current liabilities, but 150 million of those current assets is inventory. Quick ratio: (450 - 150) / 300 = 1.0. Meaningfully tighter than the 1.5 current ratio suggested on its own.
How Kobo & Cents uses it
Quick ratio and current ratio together make up the liquidity category. Reading them side by side is often more informative than either alone, a big gap between the two is itself a signal worth noticing, not just the two numbers individually.