In wiki i read "Proof-of-stake is a method of securing a cryptocurrency network through requesting users to show ownership of a certain amount of currency."
Yes POS helps is a better method for securing the netwok because it is more resistant to 51% attack. In a POW minting , if one node has 51% or more of the network's hashing power, it can possibily perform a 51% attack.
But to perform a 51% attack in POS system you'll need to have 51% of the total coins in circulation, which is highly impossible. In this case one needs to have more than 50billion coins to do a 51% atttack.