The store.exe which has been around for a while and present in previous versions of Exchange has been replaced with a managed store in Exchange 2013. It is a new concept & has been written in C#.
So what exactly is the managed store? In order to provide failure isolation in the database level in 2013, Microsoft has introduced two new processes as part of the managed store concept. First is the Store Worker Process (Microsoft.Exchange.Store.Worker.Exe) which does the same job that store.exe handled in previous versions. The only difference in 2013 is that a single Store Worker Process is only responsible for one database.
The benefit with this model is that if there is anything wrong with a single database process, it only affects that database. All other databases will be online as they are serviced by different worker processes. So, if you have 5 databases mounted, you will have 5 separate store worker processes.
I have three databases mounted on my 2013 mailbox server in the lab and there are three store worker processes running.
What about the second process you may ask? What does it do? The second one is the Store Service Process (Microsoft.Exchange.Store.Service.Exe) & it is the process that controls the different store worker processes. When a database gets dismounted, it is the store service process which terminates the store worker process that was responsible for that database. Similarly, when a database gets mounted, the store service process brings a new store worker process for that database. The store service process is a controller of all the other store worker processes.
In short, the store.exe which is present in all previous Exchange versions has been replaced by two processes in 2013 – a store service process and one or more store worker processes.