Agency: Your business.
Client: Your business' customer(s).
Agency Account: When your Agency subscribes to HighLevel you get an Agency Account in the platform. This is what you log in to when you log into your agency. The Agency Account has some unique functions, like the SaaS Configurator, that are not in the Sub-Accounts.
Sub-Account: In the HighLevel platform, your Agency Account can create multiple Sub-Accounts. These Sub-Accounts have functions that are not in the Agency Account, like websites, workflows, phone, email, products, and many more. This is also written differently, but Sub-Account = Subaccount = subaccount = sub-account.
Agency Subaccount: Where you run your Agency business.
Client Subaccount: Where your client runs their business.
Snapshot Subaccount: Where you create a reusable template for a Client Subaccount.
Test Subaccount: Where you make a subaccount just to test a snapshot you got from someone else or to see how some functions work before committing them to your main Snapshot Subaccount.
Location: This is another term for an active subaccount, often used interchangeably. Location = Subaccount.