The purpose of Move programs is to read from and write to a persistent global storage. Programs cannot access the filesystem, network, or any other data outside of this tree.
In pseudocode, the global storage looks something like
Structurally, global storage is a forest consisting of trees rooted at an account
address. Each address can store both resource data values and module code values. As the pseudocode above indicates, each
address can store at most one resource value of a given type and at most one module with a given name.