You walk down the jam aisle at the store because you need jam, and they got 20 different types in stock. So many choices, and yet, you leave without any jam in your cart.

Why is that?

It’s called the paradox of choice (or jam paradox). Instead of deciding which jam to buy, you got overwhelmed and left, scared to make the wrong choice.

If you’re the supermarket owner, and you need to decide how to stock the jam aisle, would you offer a wide variety of jam or just a handful of different flavors?

Increasing options attract more customers to the store (“Let’s go to that store, they have so much variety”), but reduces conversion. Customers get overwhelmed by the number of available options and leave, feeling overwhelmed.

If you only offer a handful of flavors, fewer people come to your store to buy jam. Those who didn’t end up buying because it’s easy for them to decide based on the available merchandise.

The same applies to your business, even if you’re not selling jam.

For instance, if you have a pricing page, how many packages do you offer right now? More than three or four? Try to concise it down to three or four.
If you close sales through conversations with your prospective customers, do you present them with as many options as possible, or do you make a preselection?
No matter what you sell, the fewer options you offer, the more your customers will move forward with the purchase. 

If you are interested in the science and psychology behind this, check out this Wikipedia page.