Goals and funnels
Name the outcomes that matter, then see where people stop.
A goal names an outcome worth counting. A funnel puts several in order and shows where people stop.
Goals
A goal matches either a path — including a wildcard, like /checkout/success — or a custom event name. Once defined, it is counted retroactively over the data you already have: you do not have to decide what matters before you start measuring.
Funnels
A funnel is an ordered list of goals. Each step shows how many visitors reached it and how many were lost since the previous one. The largest drop is usually the cheapest thing to fix.
Reading a drop honestly
A step losing most of its visitors is not automatically broken. A checkout that loses browsers who never intended to buy is working as designed. Compare the same funnel across periods before concluding anything: a change over time is evidence, a single number rarely is.