Both of these words describe substances that cause injury, illness, or death when they get into your body.
The difference is that poison gets into your body if you inhale it (breathe it in), ingest it (eat or drink), or touch it. Venom gets into your body if it is injected in, such as through a bite or a sting.
Certain snakes are venomous, because they bite you and inject their venom (although many native English speakers say "poisonous snake"). Scorpions and some spiders are also venomous, because they bite or sting you. There are plants and frogs that are poisonous - you will get sick if you touch them or eat them.
Sometimes people use poison to kill other people - by secretly putting it into their food or drink. When this happens, we say the victim was poisoned.
Pandavas: When Pandavas went in exile, they prepared for the battle in many ways. Bheema went to meet Hanuman and got more strength as a blessing. Yudhishtira learnt to excel at playing the dice game in case he was challenged and also got teachings from learned rishis. Arjuna acquired Divyastras. They turned their weaknesses into their strengths.
Kauravas: Kauravas defeated many kingdoms but created new enemies. They acquired their wealth but lost their men. They didn't prepare well for the battle.