Tibco sells integration software. Say you want to get your SAP systems to communicate with your databases, while having some logic to modify the data being passed through, then you can use TIBCO business works to connect to both and implement the logic

For Citrix, it was XenServer, XenClient, and XenDesktop when I was there? Also Go2Meeting, and a few other other stuff like that.

Myself I "grew up" in an X11 and Sun "the network is the computer" world. Have not used Citrix more than an hour, but my interpretation was that Citrix made a (huge) business out of Microsoft completely missing the network in the 90s. Both LAN and Internet. So yeah, they allow you to access a Windows computer over the net. Windows still exists so the business continues.

For Tibco I have no equivalent story to tell.

Edit: https://en.m.wikipedia.org/wiki/TIBCO_Software gives an idea.

Tibco does/did middleware. When I used it 20 odd years ago, it provided a robust messaging system for apps across the enterprise. We used it to communicate between a half dozen systems where I worked as well as the middleware for the n-tier app I worked on, and it was pretty easy to use.

Citrix is like VNC or Remote Desktop or NoMachine.

Tibco is like Apache ActiveMQ or RabbitMQ or IBM WebSphere MQ.

We used Citrix at an old corporate job. It was an all-in-one corporate networking solution. We had 2fA keys and logins and citrix was the entire IP(Intellectual Property)-protection networking + vpn layer.