What is gardening leave?

Well, based on my research it is a practice whereby an employee leaving a job—having resigned or otherwise had their employment terminated—is instructed to stay away from work during the notice period, while still remaining on the payroll.

It's when you're terminated. Your access is revoked. But you're paid for the duration the HR decides. You get relieving letter based on the duration you were in their system for aka last salary you recieved. This is rather cordial than companies who fire you on the spot and give a tiny severance. It's basically done to protect company's interest because they might feel you stand a chance of copying, taking away company's data, or for any other reason. While losing a job sucks, you're better off not working with companies that won't even provide an explanation on why you're being terminated.

Its when you get an offer from a close competitor company and resign.. the current org makes you serve notice period by blocking your access but keeping you on payroll till end of notice... i.e. you can spend time gardening , etc :) Generally happens when you are in AWS, Google, MS like places and get offer from either of the other 2...