When multiple PDU sessions/multiple QoS flows in 5G

Dear all,

I would like to know in what cases a UE and gNB will create multiple PDU sessions / multiple QoS flows within a PDU session in 5G? Also, I wonder what components in UE or gNB or core network decide to create a new QoS flow and how (based on some IP packet examination)? Thank you!

For example, based on Multiple PDU Sessions, when you do VoLTE, a PDU session is created. Meanwhile, if you do web browsing, another PDU session is created. However, do you know what specific component in the UE decides to create a new PDU session?

Also for the multiple QoS flows, who creates a new (e.g., second) QoS flow? Based on what? Is it based on some IP packet inspection? Does this multiple QoS flow concept really gets practiced in commercial operators/UEs?

Thank you!