What is the difference between Msol and AzureAD?

Could you elaborate on the distinction between Msol and AzureAD in the realm of cloud identity and access management? I'm particularly interested in understanding how they differ in terms of their functionalities, use cases, and how they integrate with other Microsoft cloud services. For instance, how does Msol specifically relate to Office 365, while AzureAD provides broader identity services across the Azure platform? Additionally, are there any specific scenarios where one might prefer Msol over AzureAD, or vice versa? Clarifying these differences would greatly assist in making informed decisions regarding cloud identity management.