What material did Henri Matisse use to create 'Les oiseaux' 'La vis' and 'Amphitrite' and what do these pictures mean?

They are all serigraphs. (If you need to know more about this technique, click link below!

The titles mean: the Birds, the Screw and Amphitrite, the wife of Poseidon, god of the sea.

Then do yourself a favor:

Do not look at art as if it were The Da Vinci Code.

Enjoy the beauty of it! That is what art is about and it is what Matisse wanted you to do.