Query Recompilation Details
SQL Server contains self-tuning functionality that will recompile your query as the source data changes to find more efficient query plans for your current data. This process of recompiling queries is a great, general-purpose feature to keep your system running well. We have a white paper describing some best practices for managing query recompilation in your server that is a good primer for learning more about how your system is working "under the covers". Enjoy!
https://www.microsoft.com/technet/prodtechnol/sql/2005/recomp.mspx
Thanks,
Conor Cunningham