For a user to be able to swap between two assets there must be a Pool for those two assets and that pool must have 'liquidity' (funds in both assets). A large amount of liquidity is required for users to be able to swap close to the mid price.
As a permissionless protocol any user can create a pool for an asset pair or provide liquidity for a pool.
There are some important considerations when creating a pool:
Assets in pools should only be currencies - assets with large total supply.
Assets in pools should NOT be collectables, NFTs, or similar assets with low total supply.
The system is designed with the expectation that the minimum input and output amount of a swap is 1000 microunits.
A small quantity of each asset is permanently locked in the pool. This amount is displayed the first time liquidity is added.
The initial liquidity must be provided at an appropriate ratio that matches the market rates to avoid losses to arbitrage.