PoB allows the miners to “burn” or destroy cryptocurrency which grants them the right to add blocks in proportion to the coins destroyed. Essentially, miners burn coins/tokens to buy virtual mining rigs that give them the power to mine blocks. The more currency burned by the miner, the bigger the ensuing virtual mining rig.
To burn, miners send currency to a verifiably un-spendable address. This process does not consume many resources, thus PoB is often called PoW without energy waste. Depending upon the implementation, miners are allowed to burn the native currency or the currency of an alternative chain, and in exchange, they receive a reward in the native currency of the blockchain.