What do Taiwanese have to do and sign to travel to China, and can active, reserve or retired military do it?

The extent of my knowledge is that when Taiwanese individuals would like to travel to China for business and/or pleasure they can not use the same passport they use for travel elsewhere. Instead they must apply to China for other travel documents specific for this purpose.

During this process I believe there is a statement that must be signed. I don't know, but my guess is that it has something to do with "clearing up ambiguities" with how One China is interpreted.

So I'd like to ask:

Question: What do Taiwanese have to do and sign to travel to China, and can active, reserve or retired military do it?

Taiwan's military has several branches of active military as well as an armed forces reserve; I'm curious if Taiwan allows them to go through this procedure.