During an IPO, Investment banks play a number of roles at different stages in the process. These include advising, managing the process and underwriting (where the bank acts as an intermediary between you and investors). The bank implements the transaction as your trusted partner.
Companies appoint several Investment banks, named as 'Banking syndicates'. Usually, one bank is named “Global Coordinator/Lead Manager”, which means it is responsible for coordinating and implementing the IPO and maintaining a relationship with the market regulator. The other banks act as Joint- Bookrunners/Co-leads; their role and scope depend on the syndicate (structuring, placement, research).
Investment banks also act as listing agents. Listing agents are all market members accredited to advise companies on listing on Euronext markets. These investment banks are the official intermediary between the stock exchange and the company for admissions on the Euronext regulated market.