Exactly what the message said.
Apparently you have an older version of Word, one which is a PPC-type application.
In Snow Leopard and earlier, the Rosetta software was used to allow PPC-type applications to be used on Intel-processor machines. Lion does not support Rosetta, so such applications will no longer work.
• Migrate to another application, one which is Intel and not PPC.
• Upgrade your version of Word to one which is compatible with Lion (i.e., one which is not a PPC-application).