1:ans:
A tree whose element have at most two children which are referred to as the left child and right child is called binary tree.thats means binary tree can have only two children.
2:ans:
In a full binary tree no node has only one child,each node has two children and full binary tree is a perfect binary tree with all leaves at the same depth.
on the other hand In a complete binary tree is like a perfect binary tree but with rightmost so many leaves removed.the attractive feature of a complete binary tree is that it can be represented in an array very efficiently.the binary heap data structure used a complete binary tree stored in an array.