SEO is the process of improving the volume or quality of traffic to a web site from search engines through search results and reach to
the top 10 position using relevant keywords.
Search engines perform several activities in order to deliver search
results – crawling, indexing, calculating relevancy, and retrieving. First, search engines crawl the Web page to see what is there. This task is performed by a piece of software, called crawler or bots.
Digital Marketing is the promoting of brands using the Internet, Mobile and other Interactive channels.
SEM is broader than SEO. It includes SEO and paid techniques like paid listings and paid inclusions to improve a sites visibility in search engine results.
White Hat: Building quality content towards SEO. Relying heavily on the advantages of quality content and effective marketing strategies to achieve top rankings. This tactics are considered totally safe.
Black Hats: Spamming occurs when someone creates websites that are targeted at tricking and manipulating search engines and thereby get irrelevant or poor quality search engine result pages which is not recommended.
Grey Hats: This includes both white as well as black hats, Gray hat SEO includes things like publishing duplicate content. Multiple, otherwise white hat, sites that have the same content. Gray hat SEO also includes mild artificial linking schemes.