In complete binary tree, every level is completely filled with the exception of bottom level.
In strictly binary tree, every node has either zero or two child nodes, i.e; no node can have one child node.

Consider the following binary tree:
3
/ \
2 1
/
4

Now this is complete binary tree as every level is completely filled except the bottom level (bottom level can be completely filled but it is not required). But it is not strictly binary tree as node 2 has only one child.

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Consider this one:
3
/ \
2 1
/\
4 5
This is complete binary tree and also strictly binary tree.


And this binary tree:
3
/ \
2 1
/\ /\
4 5 6 7
It is also complete binary tree and also strictly binary tree.

But this binary tree:
3
/ \
2 1
/\
4 5
/\
8 9
It is not complete binary tree as every level is not completely filled, node 1 does not have any child nodes. It is a strictly binary tree as every node has either zero or two child nodes.