What is the concept of the Union of FA’s ?

When we take Union of two FA’s it means that resultant FA’s should accept all the words that were accepted by the two FA’s individually. It is like taking union of two sets, the resultant set contain members of both sets.
For example
Let A ={1,3,5,7,9} and B = {0,2,4,6,8,10}
then, A U B = { 0,1,2,3,4,5,6,7,8,9,10 }
you can see that A U B contain elements of both sets similar is the case with FA’s.