The full form of RHP is Red Herring Prospectus.
A company going public must submit RHP to SEBI atleast 3 days before the offer opening date. RHP is an extended version of DRHP which provides comprehensive industry details, company details, latest financial results, strengths and risks, along with IPO specific details i.e., offer size, IPO timeline i.e., opening and closing dates, etc.
RHP has all the important details that an investor requires to decide whether to invest in the IPO or not.
For more details please visit : DRHP Vs RHP