Bare Acts vs Textbook Definitions - Help!

Main problem hai textbook mein labour laws ka explanation. Sabhi textbook mein yah likha hai ki "Workman" ka definition hai, "koi employee jo contract par kaam karta hai". Par kya yahi definition real life mein valid hai? Kya jo employee kaam karte hain, unki employment condition, salary, benefits, sab kuch decide karta kya hai contract hi? Aur agar contract na hota, toh contract ko enforce kaise karte? Mere textbook mein likha hai ki jo kaam contractor ke paas ho, voh contract worker hote hain. Par yeh clear nahi hai ki kis tarike se unhein recognize kiya jaata hai. Aur kya jo kaam contractor ke paas nahi hote, voh kaise recognized hote hain?