If a customer visits the website of a bank, no security is required: the marketing pages of a bank are open for everyone to see, even when a user wants to make a calculation for a loan. Based on some attributes such as the computer or IP address, the marketing department can already identify their customer to give the best rates. However, as soon as the user wants to consult his accounts, additional security will be requested, for instance by verifying a fingerprint or providing a pin number.
That might be sufficient for making a small payment or updating your beneficiaries, but whenever the monetary value of a transaction exceeds a certain threshold, the system will trigger and prompt a next step, for instance by using 2 Factor authentication, a software authenticator or even a hardware token. Or whenever the transaction is initiated from an unusual location, additional verification steps might be triggered.
In the above examples, the nature of the session (account balance check, payments, update beneficiaries, location…) are all attributes of a specific context and can invoke different or additional security policies.