A seller on a forum or marketplace sells a text file with a key. The key is either:
Finding a safe, legitimate is straightforward if you know where to look. The golden rule: avoid cracked keys and keygens . The security and legal risks are simply not worth the few dollars you might save. Your best bet is to purchase a Steam key from official sources—Steam itself or authorized resellers like SEAGM or Gamesplanet—and follow the simple activation steps above. Euro Truck Simulator 1 Activation Key