Characteristics are used to allow for advanced provisioning rules for FiFo.cloud. They are only available in the Medium and Large package.
Packages that have a given characteristic will only allow machines with this package to deployed on hosts with he same characteristic.
So for example, if you set a characteristic disk to the value ssd on one host and disk to hdd on another you can now create packages that either only deploys on hosts with either SSD or HDDs.