Q:

i'm confused with the meanin of the word "предмет"

предмет=вещь? предмет=урок? 
if i got it correct in some cases it means "thing", in some cases it means "lesson"?

A:

There are several meanings of the noun "предмет"  in Russian. 

A thing:  

предмет домашнего обихода, предмет неопределённой формы. 

An object of thought, action:  

предмет спора,предмет любви.

Science or school subject:  

школьные предметы, успевать по всем предметам.

Purpose in the phrase:  

на предмет чего-то.

A:

Предмет is a word whose meaning oscillates between "object" and "subject". Предмет doesn't mean "lesson", it means the thing that lessons are in — math, literature, etc. In English, these are called subjects, so there.

