Can I save images in the postgres? How to define? Does the format matters? Can I save JPG/PNG?How?
you can save images as BYTEA data, and the format is totally up to your application, as postgres just treats it as a block of bytes. however, I generally find it easier to store my images on a file system, and just put the file path in the database.
By the way, here's a relatively recent discussion of this issue: