What flavor of SQL is used inside Microsoft Access? I don't have much Access experience, and I took on a new Access project. I can use SQL to query the Access databases.

What SQL specification/flavor is used inside Access? Is it the same as SQL Server?
For full details read the docs: Microsoft Access SQL reference

MS Access definitely is not the same as SQL Server. The overall syntax is similar as any flavor of SQL, but it doesn't have a lot of features that were added since SQL Server 2005. 

It doesn't even have some pretty basic features, like:


  
  DISTINCT aggregate function references. For example, Microsoft Access SQL does not allow SUM(DISTINCT columnname).
  The LIMIT TO nn ROWS clause used to limit the number of rows returned by a query. You can use only the WHERE clause to limit the
  scope of a query.
  


On the other hand, it has enhanced features, like:


  
  The TRANSFORM statement, which provides support for crosstab queries.
  Additional aggregate functions, such as StDev and VarP.
  The PARAMETERS declaration for defining parameter queries.
  


Window functions that were added since SQL Server 2005+, such as ROW_NUMBER, OVER clause don't exist as well.

Set of built-in functions for string or date/time manipulation are similar, but they are not the same.