Pre-mine pertains to the point of creation of some or all the cryptocurrency coin’s initial supply prior to being launched publicly. This is done instead of being generated throughout a period of time through means of mining or inflation.
Pre-mine may be used for purposes held as legitimate like crowdfunding or marketing.
What this ultimately means is that no new coins will be created within the mining process. Computers that are geared for the process of mining and have fulfilled the process are let in on rewards through digital money and with cryptos not yet premined.