[noun]、即ち + [noun] [sentence]。即ち、[sentence]
即ち means "that is", "namely": what follows is the same thing as what came before, said more exactly. It stands between two nouns or two sentences and belongs to formal writing; in modern texts it is often written in kana, すなわち.
Inside a sentence it can also sit between a subject and its predicate, saying that one simply is the other.
In conversation the word is つまり. つまり also sums up or draws a conclusion from what was said; 即ち keeps to naming the same thing again, so it does not introduce a result.