From take-off performance calculations I remember that the take-off and initial climb was expressed in a number of segments. Each segment had its own performance requirements. I presume they are described in some FAR / JAR but I don't know whether to look under certification or operational requirements.
What are the segments and how are they demarcated?
Do they differ for aircraft types (propeller vs. turbofan, number of engines?)
Are these segments used for certification, operationally or both?