When two rules describe the same element, CSS decides which one wins by a score, and that score is why a stylesheet grows harder to reason about the more selectors you use. The way to keep it simple is to write selectors that lose or win predictably, not to outscore them.
About 2 min of reading
Predict then check the winner.
Two rules, one element
Before you run it, say out loud what it will print. Then open the answer.
Narrow instead of force
Before you run it, say out loud what it will print. Then open the answer.
A class that carries layout and a class that carries appearance are different concerns, and mixing them means one cannot change without the other. Naming them separately is what keeps a stylesheet editable after six months.
Browsers bring default styles for headings, lists, and links. Setting the values you actually want at the top of the file makes the page independent of those defaults, which is what makes a design portable.
An id beats a class, a class beats an element name, and the later rule wins on a tie. Knowing the count means you can predict the winner instead of testing it, and it means a rule with an id in it is a rule nothing can override cleanly.
Putting a rule at the bottom of the file does not guarantee it wins. A more specific rule above it still wins, which is why ordering alone is not a strategy and specificity is.
The alternative to raising specificity is narrowing the selector, like .card .title instead of a forced value. A narrow selector states where the style applies, which a forced value hides.
Each one is defined here on this site. Open the entry for the full definition and the other words it points at.