Is the same thing(internally) putting conditions in a query over a view that directly on the view?
Generally speaking a simple view is the same as a query, behind the scenes the view is expanded and passed along to the query optimizer as a normal query. Such a view is an organizational tool, not a performance enhancing one. Use these sort of views to limit what data some users can access directly (if users are accessing your DB directly instead of through Store Procedures) or to simplify referencing a commonly repeated query. 

Indexed Views are a type of view for MSSQL Server implementations that can have performance implications as they possess their own unique clustered index on a subset of the underlying tables' data. This sort of view can improve performance as the clustered index is a copy of the data kept logically separate from the original tables, however it entirely depends on how the Indexed View is built. If you see references to views improving performance they may be talking about these and this option is only available on MSSQL Server to my knowledge.