You can find the definition here. In lay man terms, it is to invest in a company just before it goes for listing, usually 6-12 months prior to listing. For early stage investing, it will be called venture investing, so don't confuse a VC investing, with growth investing with pre-ipo investing. They are all different and has different risk reward profiles. The strategies are very different as well. You can have a quick comparison between the various strategies i mentioned above here in terms of risk profiles and returns.
Is Pre-IPO investing a high risk game?
Is pre IPO investing risky? Of course! In fact it is so risky ...
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