u/polyphonal's answers are good, although I'd mention that that the prevalence of postdocs varies by field - there are still plenty of fields where people go straight from the PhD to a TT (tenure-track) job. Postdocs are more typical in STEM fields. For other resources, I've heard good things about this book: The Unwritten Rules of PhD Research, the Chronicle is good for getting a feel for important issues in higher ed in the US, and The Professor is In is great for more detailed (and unflinching) observations on how to get a TT job.