Someone has a Chase Freedom card with rotating quarterly 5x categories (for the first $1500 of spend in that category that quarter).

They also have a Citi Premier card which gives 3x on "the boardest definition of travel" including gas and parking, and 2x on "entertainment" including restaurants.

Their "everything else" card is an Amex Business Blue Plus card which earns 2x on everything for the first $50k spend a year. They don't spend more than $50k a year with credit cards anyway, so that $50k limit isn't an issue in this example.

During the current quarter:

They would be using Chase Freedom at least for groceries to earn 5x.
They'd use the Citi Premier at least for hotel stays, gas, parking, airplane tickets, trains, etc, which all fall under the Premier's "travel" category.
They'd probably use the Amex Blue Business Plus for everything else for simplicity, or they could choose to use Citi Premier for restaurants and movie tickets if they valued their Citi Thank You Points more than their American Express Membership Rewards points.

But last quarter, when Chase Freedom had 5x on gas:

They would have used Chase Freedom rather than Citi Premier for gas.
Everything else would have worked the same as this quarter.


The above is an example showing both rotating categories and fixed categories. Depending on your preference, you may have cards that have both or only one kind of category. (Fixed categories are way more common than rotating categories, but 5x earning is only common on rotating categories.)


(I simplified Chase Freedom rotating categories above. There's actually more than one category typically each quarter, but some of them are harder to explain, so for the purpose of the above example I just chose the most "obvious" category. For example, in last quarter they also had telephone and internet utliities, and this quarter they also have PayPal, and both quarters they also had Chase Pay, but that only works if someone wants to use their phone to pay at stores, which not all people do.)