Managed Services is the proactive management of an IT (Information Technology) asset or object, by a third party typically known as a MSP, on behalf of a customer. The operative distinction that sets apart a MSP is the proactive delivery of their service, as compared to reactive IT services, which have been around for decades.
Typically, MSPs will have the following distinguishing characteristics:
Have some form of Network Operation Center (NOC) service
Have some form of service or help desk service
Be able to remotely monitor and manage all or a majority of the objects for the customer
Proactively, compared to reactive, maintain the objects under management for the customer
Deliver these solutions with some form of predictable billing model, where the customer knows with great accuracy what their regular IT management expense will be