Change sets are the native way to move metadata customizations between sandboxes and your production environment1. They have the following characteristics:
* Change sets can only be used between related organizations, such as those that are linked by a deployment connection2. You cannot use change sets to deploy metadata to unrelated organizations, such as those belonging to different customers.
* Change sets can only deploy metadata, not data. You cannot use change sets to transfer records, such as accounts, contacts, or custom objects records, from one organization to another2. To move data between organizations, you need to use a data loader tool or an API.
* Sending a change set between two orgs requires a deployment connection to be established between the source and the target org2. The deployment connection allows the source org to upload outbound change sets and the target org to receive inbound change sets. The target org can then deploy the change set to apply the metadata changes.
* Change sets can deploy custom settings data only if the custom settings are defined as hierarchy and not list. Also, the custom settings data can only be deployed to other sandboxes, not to production3.
* Deployment is done in a one-way, single transaction. The source org sends the change set to the target
* org, but the target org does not send any confirmation or feedback to the source org. The deployment is either successful or fails as a whole, and it cannot be undone2. References:
* Everything You Need to Know About Salesforce Change Sets
* Deployments by using change sets - Salesforce Tutorial
* Using Change Sets To Deploy Apex - Salesforce Developers