On September 16, 2020 Uniswap announced its liquidity mining program allowing users to earn UNI rewards. Pickle Finance currently participates in four of Uniswap's mining pools:
As suggested above, pJar 0.69 comes in four different flavours. Depositing one of the above Uniswap LP tokens returns corresponding pUNI tokens.
Using the deposited Uniswap LP tokens, pJar 0.69 receives and re-invests UNI rewards for you so that you end up having more LP tokens than you started out with.
All of the pUNI[x] tokens allow you to additionally earn PICKLE rewards by depositing them in the Farm.