If you are only using PayPal Payments Standard, buyers will only see a PayPal checkout button in their shopping cart. However, the PayPal Standard checkout site can usually offer a card-based payment option for buyers who don't have a PayPal account. First make sure you have taken the free upgrade to a PayPal Business or Premier account that is PayPal Verified, and make sure you have set PayPal Account Optional: ON in your PayPal account under Profile (⚙️ gear icon) > Website Payments > Website Preferences.
Once you have that set up, when a buyer clicks the PayPal checkout button in your cart, PayPal's checkout site should offer buyers the choice to log into PayPal or Pay With a Credit or Debit Card. Note that buyers cannot pay with a card that is already linked to a PayPal account. The PayPal checkout site also will not offer the card payment option if you are using PayPal Payments Pro, or if the buyer is located in a country where PayPal doesn't support card payment without a PayPal account.
If you want your cart to show a separate checkout button for card payments, you will need to add one of the other payment services listed here. In this case, buyers who wish to pay with a card would simply click the dedicated Pay With Card checkout button in your cart, rather than clicking the PayPal checkout button.