The Nasdaq National Market consists of over 3000 companies that have a national or international shareholder base, meet stringent financial requirements and agree to specific corporate governance standards.
Taobiz explains Nasdaq National Market Securities - Nasdaq-NM
This is what most people are referring to when they talk about the Nasdaq. The larger companies trade on the Nasdaq National Market, while the smaller companies trade on the Nasdaq Small Cap Market.
To list initially, companies are required to have significant net tangible assets or operating income, a minimum public float of 500,000 shares, at least 400 shareholders, and a bid price of at least $5.