@mas, @Devilclarke has a point, it was <1 min time spent reading with 1 post looked at when you posted your question. The first section of the beginners guide covers the terms HF and LF that you just asked about and I already linked that. We love to help out but help us help you once you have a clearer general understanding we can help you work out specifics and/or clear up anything that is confusing you.
EDIT: Sorry if I came across as a bit harsh here, my 3d printer was making me grumpy and that may have come across more than I intended.
righty right. i do understand that and im sorry. for me my way of fully understand a topic is talking one on one with someone or doing experments. i been thinking of this for a few years now so befor getting the chip i wanted to make sure.
If you want to experiment before getting an implant there are lots of cards and fobs with the same innards as the implants. The LF side of side of the NExT is called a t5577 chip. The HF side is called a ntag 216. Both are easy to acquire if you want to mess around. The ntags can be written to with most phones but the LF chips and more complex tasks with HF chips need special hardware such as the Proxmark3. Looking into getting some test chips might be a good option for you.
No current standard payment options of any kind are supported.
The Apex chip will be capable of payment from a technical standpoint but will need approval by EMV among other things so we do not know when that will be possible.
DT offers a service where they try to convert an existing micro bank card but that has issues such as expiry.