That's may be a little bit hard to understand from Wikipedia's explanation below, to make it simple, You can build more partitions on GPT disk, Thus a professional GPT disk partition manager software is needed when its installation is growing and will keep on growing up in near days.
"GUID Partition Table (GPT) is a standard for the layout of the partition table on a physical storage device, such as a hard disk drive or solid-state drive, using globally unique identifiers (GUID). Although it forms a part of the Unified Extensible Firmware Interface (UEFI) standard (Unified EFI Forum proposed replacement for the PC BIOS), it is also used on some BIOS systems because of the limitations of master boot record (MBR) partition tables, which use 32 bits for storing logical block addresses (LBA) and size information on a traditionally 512 byte disk sector. " -WIKIPEDIA
By the way, what's the most important thing we should concern when it comes to software?
Fortunately, Partition Expert has its enterprise-class secure program in its core. Unlike other partition software claims they are safe on their website instead of its product, Partition Expert with its disaster-protection technology and cancel-at-will technical to protect your data under any emergency situations.
To resize partition is to extend partition, shrink partition, allocated free space to one drive, merge partition, and split partition. The basic function of extend and shrink partition can make up to these functions. So we put resize/move function together as one to manage GPT partitions.
That's the way to extend F: Partition, you can extend any partition but not the last partition in Partition Expert.
What if my G: Partition shows low disk space but H: Partition with much free space in, how can I solve the low disk space alert in G: and extend F: at the same time?
Well, still we can use Resize/Move Volume function to fix this problem. So situation now becomes: F: and G: low disk space, H: much free space available.