Gateway or http

You're picking how Discord reaches your bot. Pages after this one assume you already did.

Your bot opens a websocket to Discord and holds it open. Discord can send anything happening in the servers your bot is in, from messages and joins to reactions and voice. A few of those need an intent you turn on in the portal.

discord.js caches guilds, channels, roles, and members off that connection. Its collections and helpers read from that cache, so interaction.guild comes back filled in.

Holding the connection means a process running somewhere all the time.

An http bot waits for Discord to call it. Discord posts each interaction to a URL you own, one request at a time. Discord sends nothing else.

No connection means no cache. Anything you need about a guild or a member you fetch from Discord's REST API, which spends a request from your rate limit every time.

Nothing has to run between those requests.

Start from what your bot reacts to.

Does anything in your bot happen without someone running a command? Welcoming a member who joins, logging a deleted message, watching for a keyword. All of that arrives down the websocket, so a bot doing any of it is a gateway bot.

A bot that only answers commands, buttons, and modals runs on either one. The next question is where it runs. Gateway needs a process up all the time. Http needs a URL Discord can reach.

Reading a lot of server state is a second reason for gateway, since the cache answers those reads and http spends a REST call on each one.

Most of what you import comes from @seedcord/core, which both packages re-export, so a handler often moves across on its import line alone.

The code that changes is whatever touches discord.js types. getUser returns a discord.js User on gateway and an APIUser on http, so a call into a method only discord.js has needs rewriting.

Event handlers don't work on http, since Discord posts only interactions there.

Either choice needs the same setup on Discord's side. Go ahead and create your Discord application.