Coming together federation :- It involves independent states were coming together and form a bigger unit. E.g. USA,Switzerland, Australia In this federation, all the constituent units usually have equal powers and are strong the federal government. Holding together federation :- A huge country is divided into several levels. E.g. India ,Spain, Belgium In this federation, the central government tense to be more powerful.
When many countries come together to form one nation is coming together example USA When many consitutuents states form a nation and is under one flag is called holding together example India ( 29 states holding india)