A self bot is a bot that runs under the user account. It is like a user's personal assistant that responds to their command inputs to perform different tasks. The main objective of self bot is to make things easier for the users by doing small things such as posting messages, changing user’s avatar and status, etc., on their behalf.
A self bot uses a token, or encrypted text, which is the key that all Discord applications require for connecting with the account using which the app would work. One thing to notice here is that self bots can also use functions that are commonly used by normal bots, like embeds, as they can easily access the Discord API (Application Programming Interface, also referred to the direct link between code and code being able to work on Discord).
However, Discord itself seems to be in a bit of trouble regarding the self bot. To make their stance clear when the question regarding the automated user accounts was asked, they stated, “Discord's API provides a separate type of user account dedicated to automation, called a bot account. Bot accounts can be created through the applications page, and are authenticated using a token (rather than a username and password). Unlike the normal OAuth2 flow, bot accounts have full access to all API routes without using bearer tokens, and can connect to the Real Time Gateway. Automating normal user accounts (generally called "self-bots") outside of the OAuth2/bot API is forbidden, and can result in an account termination if found.”
In other words, Discord provides a bot account for automation that has complete access to API routes, meaning they can easily work in real-time. But these self bots can only be used in OAuth2/bot API, or else Discord can terminate the user account.
Though self bots can perform various tasks by just bypassing the normal user authorization and lighten user’s burden, as Discord is clear it’s against their rules. So, it is better to take the safer road then getting banned.
You can create Discord bots that can perform useful automated tasks and bot commands on your server, which are within Discord’s policy. If you are looking to create a Discord bot, you can use the no-code platform Appy Pie Chatbot. The chatbot builder has all the necessary features required to build a fully functioning Discord bot from scratch.