"Social Media" generally became popular where people used sites such as "Friendster"(2002) and "MySpace"(2003) to update relatives, friends and associates about their personal lives and find others with similar interests.
It then branched off to live Interactive video calling software Skype (2003), to now popular sites/apps such as "Facebook" (2004) and business related social media, "LinkedIn (2003).
2003 - 04
Later in 2005, "YouTube" (2005) created a whole new outlook for sharing media through the use of creating edited video / audio content. Forum based websites such as "Reddit" and social following platforms like "Twitter" (2006) were introduced as well.
2005 - 07
Social corporations then decided to take a different approach with by introducing sites such as Tumblr (2007) aimed towards photographers, models and teens, WhatsApp (2009) catering toward close family / associate conversations on mobile to lifestyle minded interested audinces with Pinterest (2010).
2007 - 10
2011 - 15
We then began to see a trend, catering toward teen/youth audiences such as "photo/following" platform "Instagram" (2010) for well known influencers to teens and young adults, and teen/youth intended photo sharing "Snapchat" (2011) to a little bit of the gaming community with "Twitch" (2011).
After seeing almost everyone on social media, apps/softwares for the gaming community such as "Discord "(2015) became more prevalent. And in the future I guess we will see more social media platforms for those interested in specific categories such as Food, News,, Health...etc. will come into play.