"CB" means Carte Bancaire — the French bank card network. Foreign Visa/Mastercard work almost everywhere, but with quirks: the €50 sans-contact limit, market stalls that don't take cards, and terminals that default to the French "débit" prompt.
Three things confuse foreigners: 1) Some terminals default to "débit" (checking account, no fees) vs "crédit" (credit, may have fees). 2) Sans-contact limit is €50 (was €30 until 2020); above that, you must insert. 3) Markets are often cash only — even big markets.
Also: foreign cards sometimes get rejected at unmanned terminals (parking meters, vending). French cards have a 4-digit PIN; American cards may not prompt for PIN at all, which some French terminals can't handle.
The short answer for your specific card type and venue, with the failure mode if it doesn't.
Insert vs tap, debit vs credit, and the exact prompt in French you should know.
Cash backup, ATM location, alternative card.
For foreign cards: "Crédit" usually wins (foreign bank charges via credit processing). For French CB cards: "Débit" is normal; "Crédit" delays the charge to month-end (sometimes fee). Pick what your card supports; if unsure, "Crédit" is the safer default for foreign cards.
ATMs (Distributeurs de billets) are everywhere. Look for BNP Paribas, Société Générale, Crédit Agricole, La Banque Postale branches. Most accept Visa, MC, Cirrus/Maestro. €1.50–€3 fee per withdrawal from your bank. Withdraw €200+ at a time to minimize per-transaction fees.
France's Vigipirate plan occasionally activates anti-terrorism measures: shopping center entrance checks, bag inspections at museums, no bags at some monuments. Doesn't change payment. Always carry ID.