Identity:

Your Nostr identity becomes yours from the moment you generate your key pair. The two parts each provide unique perspective and functionality. (Remember, there is no central entity to issue these key pairs. You can screw up and start over. You can maintain multiple key pairs for different purposes. If all of this is new and unfamiliar, start simply with the intention of trial and error.)

Half of the equation is your nsec. As long as you maintain control of that secret key, the identity is yours. You will use it to sign the notes and events that you create on Nostr. You will use it to access functionality of various tools and apps. You can use it to send monetary tips for content you find valuable. The reputation that you build through posting & interacting on Nostr will signal to others what type of person or profile this is, whether it's a genuine person, a bot (good or bad), a collection of works, etc. You might come across information that compares your nsec to a password. While a fair comparison, its important to remember that passwords can be reset, but your private key CANNOT. Lost access or control of your nsec means a loss of control over that identity. When you have decided to establish a more permanent identity, write it down, keep it safe, and use the appropriate security tools for interacting online.

The other half of this equation is your npub. This public key is used to find and display your notes and events to others. In short, your npub is how your identity is viewed by others and your nsec is how you control that identity.

Npub can also act a window into your world for whoever may choose to view it. As mentioned in a previous entry, npub login enables viewing Nostr's notes and other stuff in a read-only mode of any user's follow feed. Clients may or may not support this, some will even allow you to view and subscribe to these feeds while signed in as yourself via this function. It the basis of the metadata for your profile, too.

Profile:

Profile, in general, is a collection of things about you, which you have chosen to share. This might include your bio, chosen display name, other contact information, and a profile photo. Similar to traditional socials, veiwing Nostr profiles often includes a feed of the things you have posted and shared displayed as a single page. People will recognize you based on the aspects of your profile more than they will by your actual identity since an npub is a prefixed random string of characters . Your npub bridges a gap between strictly machine readable data and your human readable name, but it is not as simple as a name and picture. You will choose your photo and display name for your profile as you see fit, making you recognizable. These aspects are easy for copycat scammers to leverage, so your npub will help your friends and followers to verify that you are you, in the event that someone should try to copy your profile.

The Nostr protocol has another profile aspect that is important to know about, but as a general user, you shouldn't have to worry much about it. This is your nprofile. It combines your npub (or the machine readable hex verison of it) with hints to what relays you are using to publish your notes. This helps clients, crawlers, and relays find your stuff for your followers. You may notice nprofile when you share a profile link or used in other actions. When you update your relay list, your client will adjust your nprofile and send a new copy to the appropriate relays. If your believe that a client is not doing that correctly, you can visit metadata.nostr.com and manage it yourself.

Account:

Across Nostr, it is common to see the term 'account' used to refer to the combination of your identity and profile. It is a relatable term, though it may imply that some account issuer exists, but no one issues a Nostr account to you. You create and maintain it yourself.

There are situations where a traditional account will exist, such as with media servers, relay subscriptions, custodial wallet hosts, or NIP-05 providers. These things will almost always be paid services and storage that you choose to use. (Reminder: all of these things are possible to DIY with a little knowhow and an old computer)

What Is The Right Terminology?

There is no simple or correct answer here. Developers and writers will use whatever terms fit their scope and topic. Context will matter, so it's important to differentiate by that, more than any actual term.