A lot of time students get confused between Process Builder,Workflow, and Visual workflow. So today I am going to cover  the differences in all three and also which one to use when. I hope this blog post will help you.
Let’s start with Process Builder:
Process Builder:
Salesforce recently unveiled the Lightning Process Builder. This is the one of the best tool salesforce introduced because it opened up lof of opportunities for Salesforce administrators and consultants to build complex processes with just a few clicks, without writing any code. That’s powerful.
Most powerful features of the Lightning process builder are:
1) Great functionality: The process that took 10 different workflows for different outcomes, now the same thing can be done with just one process. This is because of the if-else criteria introduced in Process Builder.So you can define different set of actions for if and another set of action for else.In addition to multiple outcomes, the number of actions that we can perform has also increased. Now we can post to chatter, update record, assign tasks, create records at the same time.Process builder also allows to setup default fields for automatically created records.
2) Process builder also has a powerful and easy to use UI (User interface): You can add multiple workflows based on different criteria. Process builder are way more powerful then workflows.You can build complex processes using Process Builder.As you can see in the diagram, we have different workflow based on different criteria. In the above flow diagram, I am working with an account object, and the criteria that i have is ( if the account type is Prospect) if that’s true, then I have added an immediate action of creating an opportunity.

When you click on create Opportunity, another tab will open where I can set my default fields.
Similarly, I can add another action if it didn’t meet the criteria.

In addition to great functionality and powerful UI, process builder can do a lot more than workflows.
Workflows can only handle four types of actions:

• Updating a field.
• Assign task.
• Sending email alerts.
• Outbound messages.

But with process builder you can do additional things like:

• Quick action creates or updates record or log call.
• Update any related record .
• Post to chatter.
• Launch a flow.
• Submit for approval.

If you have additional actions to perform, you can also call Apex class from a process.
Visual workflows:
With visual workflows, you can automate the business process by building flows and pass them to the right users or systems. A flow is an application that interacts with salesforce database, execute logic, call Apex classes and also collects data from users. Using Cloud Flow Designer you can build flows.
Flows may or may not require user interaction.You can use a wizard or UI for data entry or you can also run this in the background. With Visual workflow, you can automatically transfer records when the role of a user changes.
Limits for Visual Workflow:
Max. Number of versions per flow: 50
Max. number of executed elements at run time: 2000
Max. number of active flows and processes per org: 500
Max. number of flows and processes per org : 1,000