Why does wordpress template seem to negate html code?


Ive been creating websites in html/css and by help of wordpress sometimes. Talking of wordpress templates there are some concepts which i do not grasp.  Wp templates are made of php files and have their own coding like instead of


i have to write following to include an image:


why doesnt simple html code not work and why for example does following tweak of the wp template code not work for me(to center image) ?


Obviously im not that familiar with wp templates codes as i would like to be is there a comprehensive literature to gain this knowledge (the wordpress codex page is not comprehensive enough imo and at my level


Provided your containing element is wide enough and has the correct display attribute