How do I… · Figma
A component is one master and any number of instances. Editing the master changes every instance, which is the entire point and also the thing to be careful about.
Button/Primary, Button/Secondary. Figma groups them by the part before the slash.Anything you override on an instance — text, colour, a hidden layer — sticks, and survives changes to the master. That is usually what you want, and occasionally it means an instance quietly stops matching; right-click → Reset all changes puts it back. Publishing to a library is what makes components available in other files.
Faster than searching: box the part of your screen you cannot work out and ask about it directly — in Figma or anywhere else. Answers arrive where you drew the box.