Helm Charts are simply Kubernetes YAML manifests combined into a single package that can be used to deploy an application, or one component of a larger application.
A Helm chart can contain any number of Kubernetes objects, all of which are deployed as part of the chart. A Helm chart will usually contain at least a Deployment and a Service, but it can also contain an Ingress, Persistent Volume Claims, or any other Kubernetes object. Charts are created as files laid out in a particular directory tree. They can be packaged into versioned archives to be deployed.