Generally the term is used only for games that have an online component. Essentially free to pay (aka: F2P) is an online game (sometimes a downloadable app) that has no up-front costs for playing.
That means you don't have to pay anything to install the client on your system, and there's no overt monthly fee to get access to the game servers.
However, such a game can (and almost certainly will) have some other way to collect money from you on a voluntary basis. These run the gamut from online stores and subscription options offering cosmetic items to intrusive in-game solicitations for things that are essentially required to have any success in a reasonable amount of time.
A business model where there's no subscription option to give you access to everything is called "freemium". Freemium games are still technically F2P if they are still playable without paying anything.
However, when you get down towards the bad end of that spectrum, players have other terms they use. For example, a game that is on paper F2P, but in reality not realistically playable without paying something, is called "pay-to-win" (P2W). This is a moniker bestowed on a game by players. It is not a positive term, and you will never see it being claimed in marketing material.
A P2W game is not considered real F2P, no matter what the game's owners may claim. The two terms are effectively mutually-exclusive, although different people will use them for the same game sometimes.
"Freeware" (and "abandonware") are terms used to describe software in general, not just online games. So they really don't belong to the same taxonomy.