Polymer just means 'many monomers'. Monomers are molecules that bind together to form polymers.
For example, many monomers of glucose can chemically bind to form the polymer, starch. You can think about the little lego blocks as the monomers and when you connect many together, you form the polymer

Isomers are molecules or compounds that have the same molecular formula but different structural formulas. So they are made up of the same atoms, but these atoms are arranged differently. Once again, you can think about lego. With the same number and kind of blocks, you can create many different shapes. In this case, the lego blocks would be the atoms, which form the molecular formula, and the way you asssemble them, would be the stuctural formula.
Because of the difference in arrangement of the atoms, in many cases, isomers do not share similar chemical properties.
Look at the the difference in structures of
butane and
iso-butanehttp://butane.wikispaces.com/file/view/Isobutane.gifBoth are made up of 4 carbon atoms and 10 hydrogen atoms, which are arranged differently
Hope that helps
