The kernel uses virtual memory areas to keep track of the process's memory mappings; for example, a process has one VMA for its code, one VMA for each type of data, one VMA for each distinct memory mapping (if any), and so on. VMAs are processor-independent structures, with permissions and access control flags. Each VMA has a start address, a length, and their sizes are always a multiple of the page size (PAGE_SIZE). A VMA consists of a number of pages, each of which has an entry in the page table.
Memory regions described by VMA are always virtually contiguous, not physically. You can check all VMAs associated with a process through the /proc/<pid>/maps file, or using the pmap command on a process ID.
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