You're right Onenski that I don't think we have had too many discussions in the past on this topic. I personally have not made myself an expert on the different theories that get packaged under the name "determinism" so (since it is late when I write this) I will see if others answer first before I reply further myself.
I guess the key to unwinding this is going to be figuring out if this makes sense, which intuitively seems hard to follow:
? A determinist thinks that every event, including our decisions, is determined by previous states of the universe (out of our control). Every thought, decision and action is determined by too many factors (a good example is in the book "Behave" by Robert Sapolsky), but we don't know all of them. However, determinists consider our agency as part of the causes in the world. Whatever we do has consequences in the world. So, there's room for personal decisions. The future is unknown for us, but we are part of the causes that determine it