I want to know more about compression

The most popular and industry accepted compression technique for Black and White Images (only for Black and White and not for Grayscale or Color) is CCITT G3/G4 compression.

This is the same compression technique used in the Fax machines. G4 is 2 dimensional compression technique.

The issue with Grayscale images and Color are those cannot be compressed using this standard, Hence there are various other compression techniques used by Grayscale images such as LZW  etc and Color images are normally compressed using JPEG standard.

One thing to notice is the compression technique and file Types are two different things, therefore a image scanned in black and white may be compressed with CCITT G3 or G4 compression and saved as a TIFF file. Similarly an Image scanned in grayscale can be compressed with LZW and save as a TIFF file as well. A color image may be compressed using JPEG compression and algorithm and saved as a JPEG file as well. JPEG is a file standard as well as a compression technique.