The basic level of cloud computing is IaaS, because this is where hardware resources are made available in virtualized form. Whether storage space, processors or network – all computing instances can be added and removed again in any amount. This is why we sometimes speak of a virtual data center.

With IaaS, the cost advantages of cloud computing come into play most clearly: Hardware in particular is very expensive to purchase, outdated quickly and should also be set up under particularly secure conditions (keyword: data center vs. company basement). If the IT resources are provided in a virtualized and needs-based manner, users usually save enormous amounts of money.

Source: https://www.global.de/blog/iaas-paas-saas/