Update _index.md

Author: tengqm

content/en/docs/concepts/overview/_index.md

@@ -122,6 +122,7 @@ Let's take a look at why Kubernetes is so useful by going back in time.
 ![Deployment evolution](/images/docs/Container_Evolution.svg)
 
 **Traditional deployment era:**
+
 Early on, organizations ran applications on physical servers. There was no way to define
 resource boundaries for applications in a physical server, and this caused resource
 allocation issues. For example, if multiple applications run on a physical server, there
@@ -130,7 +131,9 @@ the other applications would underperform. A solution for this would be to run e
 on a different physical server. But this did not scale as resources were underutilized, and it
 was expensive for organizations to maintain many physical servers.
 
-**Virtualized deployment era:** As a solution, virtualization was introduced. It allows you
+**Virtualized deployment era:**
+
+As a solution, virtualization was introduced. It allows you
 to run multiple Virtual Machines (VMs) on a single physical server's CPU. Virtualization
 allows applications to be isolated between VMs and provides a level of security as the
 information of one application cannot be freely accessed by another application.
@@ -143,7 +146,9 @@ resources as a cluster of disposable virtual machines.
 Each VM is a full machine running all the components, including its own operating
 system, on top of the virtualized hardware.
 
-**Container deployment era:** Containers are similar to VMs, but they have relaxed
+**Container deployment era:**
+
+Containers are similar to VMs, but they have relaxed
 isolation properties to share the Operating System (OS) among the applications.
 Therefore, containers are considered lightweight. Similar to a VM, a container
 has its own filesystem, share of CPU, memory, process space, and more. As they