The usage of apex:param in Visualforce Page

<apex:param> tag is used to pass values from JavaScript to an Apex controller,it can only be used with the folloing parent tags.
  • <apex:actionFunction>
  • <apex:actionSupport>
  • <apex:commandLink>
  • <apex:outputLink>
  • <apex:outputText>
  • <flow:interview>

Here are some small examples of how you can pass a value via apex:param tag in Salesforce.

Use <apex:param> in <apex:actionFunction>

ApexParam.page

ApexParamController.cls

Use <apex:param> in <apex:actionSupport>

ApexParam.page

ApexParamController.cls

Use <apex:param> in <apex:commandLink>

ApexParam.page

ApexParamController.cls

Use <apex:param> in <apex:outputLink>

ApexParam.page

Use <apex:param> in <apex:outputText>

ApexParam.page

Use <apex:param> in <flow:interview>

ApexParam.page

ApexParamController.cls

See more about Set Flow Variable Values from a Visualforce Page

Enjoy It!