Header, Jpeg Or Html (Noob needs advice)

Hi folks I'm new here, in fact I'm new to web design, ecomerce and all related areas.
Please bare with me i am a compleate noob:
Currently (trying to design) a header, having very little html experiance at all the best way i know how is to use photoshop (as far as image goes) I'm quite good with photoshop and have an eye for design.
Creating and uploading a jpeg isint a problem.
The problem is this: Does my Header have to be html or Jpeg ? if i can use a Jpeg it would make life easer, but how do i attach text to it, meta tags? so the header can be read for search engines, i do have dreamweaver and photoshop, but as above I'm a compleate noob.
Any help (in laymans) with this would be appreciated and valued.
Thank you.