Or can you just use facebook pages twitter etc?
Put very simply if you want to grow your business and get more sales, customers and clients than yes you do.
Nowadays, everybody has access to the internet. Whether that be through the use of a smart phone, tablet, laptop or PC/Mac. People are surfing the web, searching and browsing for products and services they are interested in everyday.
It has now become common practice for people to go straight to Google when they are looking for any kind of product or service. Whether that be a hairdresser, local restaurant, cinema, gym or health club, massage, lawn care, plumber, roofer, painter etc. Long gone are they days of the big and chunky Yellow and White pages books. (Even these services are now online). Further more, people are also wanting to find social proof and reviews of your product or service so that they can feel confident in their buying decisions. So if you have good reviews on a site such as Yelp, you can also include a link to your businesses website, which will also increase traffic and conversions.
Put very simply, If your business or service does not have a website and you are not ranking on Google, Google local, Bing and yahoo then you are leaving a lot of money on the table and losing a lot of business.
To give you a real world example, I was searching for a local hairdresser to go and get my haircut near to where I live. So what did I type into Google? "hairdressers Ringwood" This has a Google search volume of around 70 searches per month.
Only the hair salons that had a website and were optimized for Google search and had a good SEO strategy showed up on the first page of Google. I am sure there are a lot more hair salons in Ringwood than what showed up on page 1. Maybe there is another 20-30 more but very rarely do people click past page 1 when searching for a product or service. Quite often the websites that occupy the first 3 places on Google are generally associated with having the "best" product or service. Which may not be the case at all. But they are sharing a large portion of those 70 searches per month for "hairdressers Ringwood."
Your website should act as your permanent online salesperson that does most of the selling for you. It should be optimzed for certain Google keywords or search terms that will generate leads, income and businesses for you. Your website should have a conversion strategy where potential customers are compelled are do want to enquire or do business with you. If your website is old and outdated and people want to leave as soon as they visit your site, then this will not only lose you a sale but also Google will penalize you for one of their ranking factors knows as 'bounce rate.' Which is basically a fancy word for how engaged your web visitors are and how long they stay on your site.