From now on, this is the branch , all dhamma I can relate to you. That is because I am a Theravada Buddhist. All I know about Mahayana are the information I have read about it. You also can find them searching internet. That’s how I read about it most. (How you find something does not matter, if it is helpful to you)
When lord Buddha existed His holiness had prescribed some rules that sangha should follow.(These are called vinaya).These were for the long survival of Buddhism.
But some time after ‘ his holiness Buddha ‘ had passed away, senior arahat bhikkus noticed that some of the monks, who had not achieved any stages of enlightenment, had started to ignore these rules.
So elderly arahat sangha lead by “Maha kasapa thera” arranged a convocation with the support of the king Ajasath( an Indian king). This was after three months of his holiness Buddha’s parinirvana( death). Only enlightened bhikkus : arahats had participated in this convocation. These venerable arahat sangha discussed all dhamma they had heard from his holiness Buddha. They had categorized these teachings accordingly.
Decisions were made how to keep the knowledge available as long as possible. That was, senior bhikkus and their student generations, should take care of the section of dhamma they were entrusted with and learn it by heart. This kept collected Dhamma at that convocation.
Some Bhikkus at that time had not agreed with these decisions and had kept to their own ways. Followers of the decisions protected dhamma with them generation by generation. this group is called known as Theravada.
Theravada can be considered as more closely to what was taught by his holiness Buddha at about 550 BC. venerable Theravada sangha had remained to learn everything by heart as they have agreed. But in Sri Lanka when a rough time had arisen some centuries ago, venerable sangha in Sri Lanka had discussed and converted Tripitaka in to writings. These were written on some dried leaves from a native tree that was used for papers at that time with a native ink. I don’t know how it is in the other Buddhist countries, but it i o in Sri Lanka.
Note: This blog would be mainly on this branch.