Question
what is makraj?

Answer
The Arabic word written in transliteration in English as makhraj means articulation point, or the specific area a letter is articulated from. 
To read about the different Arabic articulation points please see: http://www.abouttajweed.com/articulation-points-areas-of-the-arabic-letters/places-of-articul.html, the whole chapter can be followed by clicking on the "next" link at the bottom of each page.