In simple terms, Paraswap is a liquidity aggregator and optimized to facilitate highly optimised swapping of tokens.
ParaSwap connects to most major decentralized exchanges, such as Uniswap, Kyber, Curve, or the 0x network. When you input a trading pair on ParaSwap, for instance, ETH to DAI, ParaSwap compares the available rates for the pair on each exchange also accounting for your transaction's volume.

It performs operations like :

• Splitting order across several decentralized exchanges, to reduce slippage
• Auto routing to explore every relevant path - to optimise gas spent
• Allow once and for all - to reduce gas expenditure on approval transactions for multiple DEXes

This mean, Paraswap relies on other DEXes for its functioning. Since it chooses optimum DEXes to route the swaps, this means, Paraswap DEX aggregating data is a good means to measure the quality of a DEX, as Paraswap , inorder to tick the above conditions, will choose the DEX with the lowest price which is usually a result of deep liquidity (shallow pools suffer larger price movements), least gas usage ( a result of optimized swapping mechanism). Hence is a good means to choose the popular DEX protocol on Ethereum.

In terms of swap, Uniswap is the leader, with Sushi and Curve following it. Uniswaps deep liquidity is a significant factor in tipping this. Curve being limited to Stablecoin swaps alone reduces its use case scenario.

Despite coming 3rd in Swap Volume, Curve comes second in USD volume due to its slippage resistant large volume stablecoin swaps.

What has the monthly volume on Paraswap been ?
In order to gather the data without duplicating the USD volume due to routing, we need to understand how Paraswap aggregates a swap.

First a User sends his funds to the Paraswap Router contract. The contract then chooses the routes, does the splitting. Once the funds are swapped in their respective splits and route, it returns to the Router contract. Tracking the returning of funds to the originator address from the Router contract will allow us to gauge the swap volume

We can see that most of the volume has entered paraswap during the Market's recovery phase. Since the turn of the year, Paraswap has seen diminished volume. However, this is probably a general market condition as, Ethereum was mostly in hibernation, with less activity and sub 30 gas prices.