File Formats

1.  JPEG, GIF, PNG, HDR, and RAW.
2. In a raster image, the data describes the characteristics of each individual pixel, in a vector image there is a geometric description which can be rendered smoothly to any desired size.

JPEG
1. Lossy
2. Small images and online (i.e. Facebook, twitter, etc.)
3. yes

TIFF
1. Lossless
2. working format or editing digital images
3. yes

PSD
1. Either lossy or lossless
2. photoshop documents; layers with masks, transparency, text, etc.
3. no

NEF 
1. Losslesss
2. when making large images, or you just want better quality/more editing options.
3. yes