This is so easy but so important. It is possible to snoop in on communications over the Internet. So what about, when your customers are typing sensitive data into your site?
In reality this is more about protecting your sales than customer data. Nowadays customers are quite sophisticated and if they don't see a reassuring padlock icon or notice that the address is http instead of https when filling out forms, they will probably quit and buy elsewhere.
SSL will ensure that the private information the customers share with you, will be encrypted during transit.
Order an SSL certificate from your hosting provider by buying it from their website or giving them a call. It shouldn't cost more than $50 a year ...