Internet marketing is essential for any business which is keen in expanding its presence or visibility over the globe. There are three major online marketing strategies have been evolved till, namely SEO, PPC and SMO.
SEO (Search Engine Optimization) is the most effective and best digital marketing strategy among these three. SEO enhances your website ranking in the search engines' results for the keywords that your business belong to. For example if you provide plumbing services in New York and if you want your website to be ranked on the first page in the google results, if someone searches "Plumber New York", then SEO can help you.
PPC is pay per click advertising where you pay a amount to be appeared in the search results for the keywords you decide.
SMO is social media optimization which uses various social networking sites to enhance your brand awareness among people.
For more detailed information and pricing guidance, you can contact to companies that provide online marketing services. One I know is LikeIn Infotech in India. You may refer their website: http://www.likein.org
I hope this information is useful to you.