what type of data found in mdf and ldf and ndf files

when create database in SQL server 2008 it contain three files

mdf

ldf

ndf

what i need to ask what type of data saved in mdf and ldf and ndf

to be more clear see example following

if i have HR DATABASE

and inside HR database i have table employee

table employee have FOUR fields

ID

NAME

ADDRESS

PHONE

data inside table as following

ID NAME ADDRESS PHONE

1 MARTEN CAIRO 01222222

2 WILSON USA 0765444

3 MICHEL FRANCE 0997766

my question

IN which files(mdf,ldf,ndf)

saved records of data

in which   files(mdf,ldf,ndf) saved fileds and table object without data

table employee have FOUR fields

ID

NAME

ADDRESS

PHONE