When an employer recruits an employee, they are bringing that person into their organization to do a job for an agreed amount of money. Effectively they are paying you in exchange for your time.
If we look at this another way. You go to a store and buy a product. If the product is faulty or does not do what it was advertised to do / meet your expectations, you will often return it to the store to be replaced or to get a refund.
Now using that analogy and imagine you are that product. This is exactly the same as being an employee. The employer “buys your time” in good faith in exchange for deliverables that you have agreed upon..