These days, there are applications for everything. Collaboration software, internal wikis, ticketing software, learning management systems, content delivery systems, chat software, sales tracking, blogging, email, video conferencing and more. There are even applications that keep track of your other applications.
If you have the money, you can pay for licenses and support for each of these applications, which typically ensures that they will "plug in" to each other smoothly. If you're trying to save a dime and you opt for the free, open-source versions, then the integrations (if they exist) won't be as mature, and there isn't any support if you run into problems. Often all you get is a long wiki page describing three or four hundred API endpoints.