Gearset will work for any cloud that builds on core Salesforce.com platform, previously known as Force.com, using the Salesforce metadata format. This includes:
Sales Cloud (the core CRM of Salesforce)
Service Cloud
The Salesforce Platform
There are several Salesforce clouds that are actually entirely separate products, built on different underlying infrastructure. Gearset will not work with these clouds:
Marketing Cloud
IoT Cloud
Commerce Cloud