Proportional – When a block is found, the reward is distributed among all workers proportionally to how many shares each of them has found.
PPLNS – Pay Per Last N Shares. Similar to proportional, but instead of looking at the number of shares in the round, instead looks at the last N shares, regardless of round boundaries.
PPS – Pay Per Share. Each submitted share is worth a certain amount of litecoins. It is risky for pool operators, hence the fee is highest.
RBPPS – Round-Based Pay Per Share. Like PPS, but payouts are delayed till a block is found and confirmed by the network. If a found block gets orphaned, earnings relative to it are not paid.
SMPPS – Shared Maximum Pay Per Share. Like PPS, but never pays more than the pool earns.
RSMPPS – Recent Shared Maximum Pay Per Share. Like SMPPS, but aims to prioritize the most recent miners.