Web Development is the skills and work of creating a website from scratch. This includes design to software program development. Usually you start by developing a graphic design of the website and a list of requirements and features for the website. After this, the real coding begins and all of the previous designs and features of the website are implemented through programming.
Software engineering is more aimed towards the development of task specific applications. For example, say a Farm Business wants an application which can count inventory and update it everyday as more crops are harvested. Imagine that this application also needs to be able to group crops by date, type, purpose, and GMO specification. One would have to develop a specific application that specifically serves this purpose and is the best at accomplishing such task.
Social Media Marketing
The use and constant management of social media platforms to promote a product/service. An example could be constant posts about your product/service and current updates to such product/service. Another example could be a Facebook Ad about your product/service on a sale your business is having for a holiday.
Android App Development
Android App Development is the creation of Android Applications, from idea, to having a fully functional public app on Google Play.