I also don't remember having a lesson on the tamtego group of words, but at one stage they started to appear and I gradually understood that they mean "that", and differ by gender, number etc. My brain too, felt it couldn't cope, as I couldn't work out the logic behind which form was which, and I just had to keep guessing. Following that, the group of similar words without the "tam" prefix also appeared, and I soon learnt (by the effective "stick" method of having to keep repeating exercises!) that they mean "this". So they both sort of stand in for "the" but are more specific. An example of how we could do with more "tips and notes" on grammar?