CI in this context is apparently "Continuous Integration", referring to a mechanism by which the members of a software development team can merge (i.e., integrate) their individual work with work done by others. "Continuous" because the mechanism allows the team to build and possibly deploy the product with each new change.

I think CD is "Continuous Deployment".

So, yeah, kinda like a source code control system, but including a build engine and other things. Hosted, as jkl says, on a server.

I'm not sure, but the acronym seems to have been introduced by the Agile community.

Nothing specific to Unix, obviously, and I suppose I should apologize for bringing it up here. I just got annoyed by the cryptic in-group language and how much effort is needed to penetrate it. Failure to define/explain our terms or provide links to background material is fairly common in tech and often obfuscates what turns out to be a rather simple (perhaps even obvious) idea.

One of the things I love most about Unix is that its originators wrote so clearly about what they were doing. I admire Kernighan and Pike, for example, as much for their writing skills as for their programming chops.