The basic should be the concept not the daily activity, to do the day to day job someone must now why he/she do the job and why that job can effect the company in short and long term. The concept of Digital Marketing is something like an umbrella that connects with other divisions. I make a drawing as follow just to make it simple and understandable.
In a brief most of the digital player need a home can be mentioned as Website in this case.
Website
A website is a domain with compilation of files inside a web hosting that can be viewed using web browser. This website contains all the information a customer or prospect need, not only information it is also can be something interactive and processing orders. Everything happens here where the customer and the seller meet.
IT
A good website should be properly functional in it's features, payment gateway, security, etc. There is no room for technical errors otherwise it will damage the reputation and sales. An example is when someone want to make a purchase unable to press the checkout button for some reason then cancelled the transaction, this is a lost sale.
Digital Marketing
When IT did a good job maintain the website, then it comes to the Digital Marketing to spread the word out to the world on the website. So that many people will come and visit the website.
This can be done by putting the website domain name in multiple marketing channel like: SEO (Search engine optimization), SEM (Search Engine Marketing), Social medias (Facebook, Twitter, Instagram, etc), Blogs (Wordpress, Blogger, etc), Newsletter (Mailchimp, icontact, Getresponse, etc), and so on.
Digital Sales
Then what happened after the Digital Marketing pulling tons of people to the website, it comes to Digital Sales take part. Converting those people or traffic into sales, this can be done by writing a good sales copy inside the website, a good sales copy usually consist of what to offer, list of benefit and reputation so it can be trusted.
This part is also follow up with the 50:50 prospect who are not yet to decide to buy or not.
CRM
Customer Relationship Management, when customers buy from the effort of Digital Sales, we need to maintain that customers so they would love to buy it again from us. Again and again.
So that's it about Marketing and Friends i don't want to make it too long it will bored you in the end, lets connect add me to your contact list and keep in touch!