A contactless smart transit card is dedicated to paying for travel on specific transit operators’ subways, busses and trains, while a contactless credit or debit card from American Express, Discover Network, MasterCard or Visa can be used at any merchant that accepts contactless or magnetic stripe payment.

Contactless transit cards and contactless bank cards are converging in the United States, however, as transit operators are moving toward “open payment.” This enables the use of bank-issued contactless cards for direct transit fare payments without a separate transit fare card. This also paves the way for direct transit fare payments using mobile phones with Near Field Communications (NFC), which works with open contactless payments.

See also,

Can I use my contactless credit or debit card to pay transit fares?

When will I be able to pay transit fares with my mobile phone?

How does mobile payment work?

What Is NFC and how can I use it?

What cities offer smart transit cards?