initialization of lcd display

hi
sorry to ask these many questions please help.

what is the LCD DISPLAY INITIALIZATION?
WHY IT HAS TO BE DONE?
BASED WHAT ARE THE CONSIDERATIONS IT SHOULD BE DONE?
WHAT IS 4 BIT MODE & 8BIT MODE IN THIS?
IS THERE ANY OTHER DIFF. B/W 4 &8 BIT MODES & IT'S INTIALIZATION PROCEDURES?
HOW TO DO THE INITIALIZATION IN STEP BY STEP?FOR BOTH 4 & 8 BIT MODES.
IF THE OPERATING FREQ. MATTERS HERE, HOW IT IS?

Read through some of these app notes:

http://www.newhavendisplay.com/index.php?main_page=app_notes

A common LCD character display used is the HD44780. The datasheet for it is further down that same page and discusses all of the questions you have asked.

http://www.newhavendisplay.com/app_notes/HD44780.pdf
Page 23 discusses the initialization routine,
Page 32,33 talks about 4 bit and 8 bit mode

LCD Display Initialization in simple terms is just turning on the LCD so that you can display whatever string of characters you choose. Usually an internal reset circuit will come into effect and reset the LCD, so that the previous characters are erased and a new blank screen is presented. So I guess this explains why and what Initialization means in the simplest of terms.

8 Bit mode and 4 Bit Mode are ways to communicate with the LCD. Usually data is sent in either of the 2 ways. If you use 8 Bit Mode then you can transfer data at one go, if you use 4 Bit Mode then the data is transferred twice. Usually availibility of I/O pins dictates which mode is being used.

As fas as step by step instructions, if you provide some of the hardware and software details you are using, maybe I can be of some help.