There are several distinct types of lounge networks, including
Airline specific lounges
Credit card issuer lounges
Independent lounge networks
Airline specific lounges include the American Airlines Admirals Club lounges, Delta Sky Club lounges, and United Club lounges, among others. Access to these lounges differs between the programs, but they are usually reserved for travelers in first or business class, elite airline members, those with paid memberships to the lounge network, or access through certain credit card ownership (such as American Express Platinum cardholders having access to Delta Sky Club lounges while traveling on Delta flights).
Credit card issuer lounges include the American Express Centurion Lounges and newly introduced Sapphire Lounges by the Club. These lounges are accessible with ownership of certain credit cards like the Platinum Card from American Express for access to the Centurion Lounges, or, in the case of the Sapphire Lounges by the Club, sometimes with Priority Pass membership.
Independent network lounges include Priority Pass lounges, Loungebuddy and the Global Lounge Network. These networks are made up of lots of different types of lounges with varying amenities. Travelers can access these lounges through credit card benefits like Priority Pass Select membership, memberships purchased directly through the networks, or through the Loungebuddy App with purchase of individual entry to a specific lounge. Independent lounges are often the ones credit cards will provide you access to, the exception being that some airline branded credit cards provide access to the airline's specific lounges.
With many of these lounges, you can purchases day passes or even annual memberships for access. Annual memberships will run in the hundreds of dollars and day passes will quickly add up as well. If you're a frequent airport lounge visitor, even paying a high annual fee for a credit card that grants you access will likely pay off over the course of the year.
Learn more about the various airport lounge options in our guide to airport lounge access.