I’ll break it down in two ways, if you’re a programmer or know anything about programming outside a blockchain then obviously you’ve heard of let’s say production and test environment or sandbox, so when you’re making a new piece of software or some new code, before you put it in a production environment you want to test it, so you put it in a clone of your production environment let’s say for example this is a Fintech piece of software you need to test this because it’s going to be moving money and you won’t want to move real money when you’re testing because what if it doesn’t work, it’s broken or it causes a bunch of losses then you lose money. So you put it in a test environment, you have one server that actually does transaction and you have another server that mimics this server but transactions are in demo mode they don’t actually move money right? so that will be your test environment.

On Blockchain you have a Testnet which is where you test, move coins and tokens back and forth between leading accounts, you can test for throughput, how much transaction volume etc. At the end of the day none of the transaction is real and no real financial information data or money is changing hands.

On the Mainnet this is your production environment, when you put something on the mainnet you’re actually doing real transaction that are now irreversible and if you’re talking about tokens, coins or anything with some type of monetary value you’re now moving money so that’s Mainnet.