Exploratory testing vs Adhoc testing

 Exploratory testing:

https://www.guru99.com/exploratory-testing.html

This plays when you do not have supporting use-cases to understand the application. Testers first have to understand the application better and then test the application with formal test approach. 

It is defined as a type of testing where Test cases are not created in advance but testers check system on the fly. They may note down ideas about what to test before test execution. The focus of exploratory testing is more on testing as a "thinking" activity.

Exploratory testing is simultaneous learning, test design, and test execution.

Adhoc testing:

Main aim of Adhoc testing is to find defects by random checking. Adhoc testing can be achieved with the Software testing technique called Error Guessing. Error guessing can be done by the people having enough experience on the system to "guess" the most likely source of errors.

This testing requires no documentation/ planning /process to be followed. 

Since this testing aims at finding defects through random approach, without any documentation, defects will not be mapped to test cases. 

When execute Adhoc Testing?

https://www.guru99.com/adhoc-testing.html

Ad hoc testing can be performed when there is limited time to do elaborative testing. Usually adhoc testing is performed after the formal test execution.

Types of Adhoc testing:

Buddy testing: A dev and QA work together sitting side by side , This testing usually happens after Unit Testing completion.

Pair testing: 

2 testers sit together 90 mins without break. +- 45 mins if required. The testers are Experienced and non-experienced to share their ideas and views

Monkey testing Randomly test the product or application without test cases with a goal to break the system.