In a monolith they may be modules within a single application/binary instead of different services. Nobody said a monolith can't be split in modules :) IMHO,

In a monolith they may be modules within a single application/binary instead of different services. Nobody said a monolith can't be split in modules :) IMHO, a well-written monolith is like a microservice architecture but without the network layer in between boundaries.