For instance, if you are raising money for a cause, like in crowdfunding.
You need someone you can trust to hold the deposits and use them only if the baseline is reached.
Basically, an escrow is a system of holding money on a trust party that can resolve disputes and give the money back to one of the parts involved: client and provider. It is a system of deposit to provide some kind of insurance to both parties that goods and services are delivered in good condition, as required, etc.
For instance on ebay, if they didn't use an escrow system you could never claim your money back if you received a faulty product. The money was gone and there was nothing you can do. With an escrow, ebay can hold your money till you receive the item and give good feedback or somehow dispute that money for you to receive it back with some kind of intimidation.
Hope this makes it more clear.
The origin of the word escrow comes from the old French 'escroe', that means rolled up.
Just like toilet paper that makes sure no one gets out of it, so that you can use it when you need.
