The monolithic architecture is considered to be a traditional way of building applications. A monolithic application is built as a single and indivisible unit. Usually, such a solution comprises a client-side user interface, a server side-application, and a database. It is unified and all the functions are managed and served in one place.
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While a monolithic application is a single unified unit, a microservices architecture breaks it down into a collection of smaller independent units. These units carry out every application process as a separate service. So all the services have their own logic and the database as well as perform the specific functions.
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References
https://www.n-ix.com/microservices-vs-monolith-which-architecture-best-choice-your-business/
https://nordicapis.com/whats-the-difference-between-monolith-and-microservices/