How can I know the difference between generative phonology and segmental phonology?
Generative phonology is a meta-theory of phonology (i.e. the application of generative grammar to the study of phonology), but segmental phonology is the study of a specific area, namely segments, as opposed to prosody (such as syllables and tone). Thus one can study segmental phonology generatively or non-generatively, and one can study prosody generatively or non-generatively. While there is a rather hard distinction between generative and non-generative approaches to language, the segmental / suprasegmental distinction is more a matter of personal interest. Indeed, especially since the advent of autosegmental phonology (e.g. Goldsmith dissertation Autosegmental phonology), the distinction between segmental and suprasegmental aspects of representation has been blurred, so that only moras, syllables and feet are resolutely suprasegmental.