Assuming you're talking about SQL Server.
From http://msdn.microsoft.com/en-us/library/ms187928.aspx and http://msdn.microsoft.com/en-us/library/aa226054(v=sql.80).aspx
Explicitly converts an expression of one data type to another. CAST and CONVERT provide similar functionality.
So yes, they are functionally the same. They just have different syntax that allows for more complex conversions or (subjectively) improved readability.