PPS mining pool (similar to working mode) is the shorten of the Pay Per Share. PPS is calculated by the proportion of the computing power in the pool and estimates the daily earnings of the pool which gives the users a basic fixed income every day.
For example, if your computing power is 100T, while the computing power of the entire mining pool is 10,000T, you occupy 1% of the power capacity of the mining pool. Assuming that the mining pool can dig up to 4 blocks a day based on the current difficulty and global overall computing power, which is 50 BTC. According to the PPS mode, the mining pool will pay you 1% of the whole mine pool every day, which is 0.5BTC. Even if the mine pool digs only one block today, you will get the 0.5 BTC (the mine pool loses money). And if the mine pool is over-exploited and digs 10 blocks, you will still get 0.5 BTC (lucky for the pool).