Microsoft's competitors are Apple on the hardware and software front, Google on the search engine front, Atlassian on productivity tools front, GitHub on the repository/code storage front, AWS on the cloud storage front, etc. I assume Microsoft's core solutions are their OS, their productivity tools and cloud.
Google's competitors are Yahoo, Bing and Duckduckgo on the search front. Garmin, TomTom and others on the map front, etc. And perhaps everyone on the email front. Here I assume Google's core tools are search, email, and maps.
Facebook's competitors are... Instag- oh right. Uh, Snapchat, I guess?