Influencer marketing is a form of marketing in which focus is placed on specific key individuals (or types of individual) rather than the target market as a whole. wikipedia.org

Email marketing is directly marketing a commercial message to a group of people using electronic mail email. wikipedia.org

"Marketing automation refers to software platforms and technologies designed for marketing departments and organizations to more effectively market on multiple channels online (such as email, social media, websites, etc.) and automate repetitive tasks. Marketing departments, consultants and part-time marketing employees benefit by specifying criteria and outcomes for tasks and processes which are then interpreted, stored and executed by software." wikipedia.org

Marketing communications (MC) uses different marketing channels and tools in combination: Marketing communication channels focuses on any way a business communicates a message to its desired market, or the market in general. A marketing communication tool can be anything from: advertising, personal selling, direct marketing, sponsorship, communication, promotion and public relations. wikipedia.org

A digital strategy is a form of strategic management and a business answer or response to a digital question, often best addressed as part of an overall business strategy. wikipedia.org

Digital marketing is an umbrella term for the marketing of products or services using digital technologies, mainly on the Internet, but also including mobile phones, display advertising, and any other digital medium. wikipedia.org