Is Jenkins-X and Jenkins Helm chart same?
No they are different. I assume the helm chart you found installs and configure Jenkins on Kubernetes - perhaps configured with some agents to run builds.
Jenkins X is a kubernetes native implementation of CI/CD, it uses some components of Jenkins, but has a lot more to it (for example, applications, environments, review apps, deployments and so on) for running apps ON kubernetes in a CI/CD fashion. The Jenkins helm chart likely sets up a single server.
edit: in the time since, Jenkins X has evolved a lot. It is now build using he Tekton engine for pipeline by default, and has many moving parts, so is quite different from running a more classic like Jenkins master/agent setup in a Kubernetes cluster.