Is Social Media Marketing all about Facebook and Twitter or are there other aspects to it?

Hello Hussam, When being asked in an interview about social media, the interviewer does not want to know the channels used because I am assuming he/she knows that already.
This is a question being asked in most interviews and what they want to hear are "Strategies".
When it comes to social media, you could've mentioned the topics below: 1.
Advertising campaigns to drive more traffic to a website or product/service page 2.
Analyzing target audience and deciding on which platform you must be involved 3.
Parallel campaigns, for example, if you have a new product launch, how can you make sure you target people on different platforms 4.
Messaging strategies and how you can engage with your fans and followers 5.
Starting/Managing a blog and what type of articles you should generate to your fans 6.
Developing an "Online Brand Personality" and making the company/brand feel more lively 7.
Deciding on what type of content should be generated from the company (Videos, images, articles...etc) and how you can spread them across different mediums Unfortunately, most companies still think "Social Media" and "Digital" is just the cherry on top and would still prefer getting involved in traditional media so when they hear Facebook, Twitter...
they get irritated simply because they don't know how important it is.
Once you explain it properly, they will be impressed.
Good luck :)

think I would agree with the first answer by Mr. George Durzi, and I would‘ve added what means and knowledge of strategies that a PR and SM expert might use to exploit and benefit from all the available SM channels. I also believe that the shocking interviewer question could have simply been maneuvered and answered to, but the distressing feelings of the moment itself might sometimes affect the candidate’s state of mind, confidence and stability.  

1- Face Book
2- Twitter
3- Google+
4- Google Tools
5- Bambozer Application
6- Blogs

Yes, there are.
Nowadays Social media is all about interaction and any app which allows you to do it falls under the umbrella of Social media (AKA Web 2.0).
This might include your product ads/demos on Youtube, your product page on Wikipedia (or a personal one at that), any poduct visibility in Online communities (such as 2nd life), someone BLOGGING about you ...
anything.
Nowadays what you can limited to social media is limited by your creativity only.
You can read about what the Movie Hunger Games and Ariel fashion Shoot to understand more as to what else can be engaged under the guise of Social Media.

Social Media Marketing is not about depending on any platforms like Facebook or Twitter so much that if one day an incompetent intern manages to delete the FB/Twitter profile of the brand, the brand loses its online presence. 

Social media marketing is about building your brand's persona online and using internet marketing and the ease of going 'global' to such an extent that your customer in South Africa is appreciative of your brand's vision. 

SMM is not only about campaigns but it is about allowing your very distant-located customers to associate themselves with your brand even if their city does not have the brand's representative. SMM is about developing connections and building and improving relationships with potential clients and maintaining healthy contact with the existing ones.

SMM is NOT only FB and Twitter. 

yes there are. Social media is all about interaction and any app which allow you to do falls under the umbrella policy of social media.

yes i have 5000 friend on face book

social media is a platforms to connect with your audience to build your brand, increase sales, and drive website so facebook and twitter are not the only marketting platforms for that, but Riddit, instagram other fews are also available

Yes, there are several other social media platforms. Obviously they are not so famous like these ones mentioned. Some are Russians, other Chinese or even Arab ones. But even in America there are several others. For example:

• WeChat = China
• Qzone, Weibo = China
• VKontakte (VK) = Russia
• Xing = Germany
• Maktoob = Arab

there others like whatsap, and webpager

There are several other social media application other than these. So, one shouldn't depend on these only.