Viperswap has several purposes. Its main purpose is to allow you to swap between coins. For example, if you wanted to convert BUSD into ONE to use for investment or utility.
Its second use is to earn by providing liquidity. Any time someone makes a swap (see: main purpose), Viperswap collects a small fee and shares it with the liquidity providers. So, you earn value from these fees by providing liquidity.
Staking is a way to incentivize people to provide liquidity to certain pools. If you provide liquidity to one of these incentivized pools — for example, ONE-VIPER — you can stake the resulting LP token to earn additional VIPER.
And the final thing you can do is to stake VIPER tokens in the ViperPit. When you do this, you are allocated xVIPER tokens which gain in value when any transactions across the application. This incentivizes people to invest in the platform long-term.
So, circling back to your question of what’s the purpose, the answer is: it depends. It may be token swaps, investing, or both.