A security context defines privilege and access control settings for a Pod or Container. Security context settings include, but are not limited to:
 Discretionary Access Control: Permission to access an object, like a file, is based on user ID (UID) and group ID (GID).
 Security Enhanced Linux (SELinux): Objects are assigned security labels.
 Running as privileged or unprivileged.
 Linux Capabilities: Give a process some privileges, but not all the privileges of the root user.

A service account provides an identity for processes that run in a Pod.
Note: This document is a user introduction to Service Accounts and describes how service accounts behave in a cluster set up as recommended by the Kubernetes project. Your cluster administrator may have customized the behavior in your cluster, in which case this documentation may not apply.  When you (a human) access the cluster (for example, using kubectl), you are authenticated by the apiserver as a particular User Account (currently this is usually admin, unless your cluster administrator has customized your cluster).