As Christian says above, strainers and filters are basically the same thing. Simply stated, a strainer is also a filter; however, it uses a perforated plate or screen mesh to remove larger particles from a process stream.
The major advantage of a Strainer is that it is reusable. There are many different types of strainers, including Y-strainers, basket strainers and duplex strainers.
You can find strainers in almost every industry: chemical, food, water, petroleum etc