How is it a better alternative? I.e. what does it have that is better than Parallels?
Better support (communities.vmware.com is a great place and there are a lot of other resources out there), it shares 90% of the code with Player, Workstation and ESXi so a lot of resources that you find on the internet will apply to all their products. That means that exchanging VMs between their products is much easier.
They are also more aimed at professional users (sysadmins, developers, businesses) and non-Windows systems. Parallels only really works with Windows. All the advertised features will work fine with Windows. Use something else and only a few of those features are left provided you can actually run that particular non-Windows OS in Parallels. VMware Fusion is more solid and VMware also has products for Windows and Linux (Player & Workstation).
The professional features are about creating clones (full clones, linked clones), multiple snapshots, being able to virtualise ESXi/Hyper-V/etc., run code profiling apps, encrypt the vm, manage VMs on an ESXi host as well as import from and export to ESXi hosts, create your own virtual network, isolate the VM (useful when you are sharing the vm), able to import and export OVA/OVF instances and so on. Basically they allow you to use professional software and create a base VM that you can distribute and manage in your organisation as well as use it for development and testing purposes.
Parallels is more aimed at people wanting to play games in Windows. Only with the last version did it gain certain professional features similar to Fusion and it seems you now have to get a subscription from Parallels in order to use the professional features.