How to disambiguate between various meditation practices?

From what I understand, different schools of Buddhism teach different subsets of meditation techniques, or different variations of the same techniques. However, many meditation resources don't specify which technique is meant to achieve what goal, nor the source of the particular technique. There seems to be overlap and combination of techniques, e.g. observing and counting the breath in Zazen, vs. simply observing in Anapana. Some insist that you must sit a certain way, others say to just "sit comfortably." Some you must practice for two hours, morning and evening, others say 20 minutes is sufficient. Furthermore, some sources say that their meditation techniques are not compatible with others, e.g. S.N. Goenka says if you practice Vipassana, you must not practice any other technique (but, even more confusingly, he also teaches Anapana and Metta) **Could you help me understand the difference between these various techniques (how it's performed, what its goal is, advantages/disadvantages), their relationship to each other, and their origins?** **Are there any important ones I'm missing from this list?** - Mindfulness meditation - Zazen - Vipassana / insight meditation - Anapana - Metta / loving-kindness meditation - Tantric meditation - Walking meditation - Mind clearing (not sure the right name for this - instead of picking an object of meditation like the breath, the goal is to achieve a state of complete thoughtlessness) - Samatha - Transcendental meditation (I think some of these might be special cases of others, but it's not clear to me)