What's the difference between "RTC workflow" &

We see RTC flow customization and RAM lifecycle customization. what's the difference between those two? How about the license support of those two customization ?

A lifecycle in RAM is the combination of a workflow (states and transitions) with specific configuration such as:

Which Asset types/categories should use that lifecycle
In each state, what policies are to be run
In each state, who is a reviewer
When can you take a transition
...

The workflows one can select from from the RAM lifecycle page are configured in the RTC instance RAM is using - it is based on RTC's workitems.
A Std. Server license, can only use the workflows that come out of the box with RAM.
An Enterprise Server License can customize (modify/add/remove) RTC workflows