A foreign transaction fee is an added cost for purchases in foreign currency or purchases processed outside the Philippines. It can apply to travel spending and sometimes to online merchants that bill from another country.
The final peso amount may include the card network conversion rate, issuer foreign transaction fee, and in some cases merchant-side dynamic currency conversion. Paying in pesos abroad is not always cheaper if the merchant uses an unfavorable conversion rate.
Before travel, compare the issuer foreign transaction fee and avoid dynamic currency conversion when possible. The calculator on this site estimates the added cost, but the exact charge depends on the issuer and transaction date.
Next step: Use the calculators and card database to test the idea against your own spending pattern.