They're basically simple scripts that either do something they're programmed in a set pattern, or can receive a message to spam out from one terminal.

Sometimes they're for fun. Things like hourly fox or 'every frame of Breaking Bad in order', that will have some sort of gimmick they post every hour, day, or day of the week.

Sometimes they're just 'blank' accounts that people pay someone to have follow them or send out a certain message, usually to make it seem like they're more influential for when it comes to advertisements (or to participate in a sponsor promotion so that a streamer gets more money from the company advertising through them).

Then more espionage level some companies or governments use bots to try to push particular messages to shape online discussion. Although how effective such spam bot messaging is is anyone's guess. There could also be bots that use an AI to try and phish for information or perform some other scam, too.

Ah thankies for the explanation ^^
Yeah it's the letter that piqued my interest. I've heard a few people discussing how bots were used to pedal certain agendas, but wondered how much truth was in it :3
It's pretty interesting stuff!

Amor's answer is pretty good! A "bot" is basically just any program living on a computer somewhere that automatically does a job. Most of the time, when people talk about "bots" nowadays, they're talking about programs that use fake accounts on twitter / discord / social media to interact with real human beings. Those bots usually take advantage of programming that lets them recognize certain words and write scripted responses automatically.

A couple other things people use bots for:

1) Marketing: some bots are programmed to automatically look for people talking about certain topics and respond with advertisements or product recommendations.

2) Cyberwarfare: a large group of bots can temporarily shut down a website (or a specific person's internet) by flooding that website (or person) with traffic, essentially creating an artificial "traffic jam" known as a Distributed Denial Of Service (DDOS) attack.

3) Gaming: in video games where you can earn gold/gear, like MMOs, some people write bots to automatically play the game and gather gold/gear to be sold to other players (or siphoned to the botter's main account, if they play the game).

4) Market scraping: some bots are programmed to constantly search shopping websites like etsy, ebay, etc. and look for suspiciously good deals. When they find a listing that seems unusually good (usually because somebody posted it as a mistake), they will either snatch it up so it can be resold, or alert their owner so the owner can decide if it's worth snatching. (Fun Furry Fact: this is also what happened to MFF several years ago, back when hotel rooms were sold first-come-first-served instead of using a lottery system! People wrote bots to spam the hotel website until the rooms became available, then the bots quickly snatched rooms up the second they were available!)

I'd been followed on twitter by a handful of "overly normal" looking accounts, like, the kind of profiles that definitely wouldn't be interested in furry art XD I wondered if they were potentially bots.
Thanks so much for the explanation! I actually like the sound of the little gaming bots that go foraging for loot!! haha.

Taken with amon-enkaire's answer, this covers pretty much all of the common uses of the term. I'll add just a couple other examples of bots to the pile:

Web crawler
These bots are really important and helpful for finding things on the internet! They're the whole reason search engines like Google work at all. Web crawlers systematically "crawl" through the internet to index websites, so that these websites can appear in search engine results. Without web crawlers, search engines like Google would have no way of knowing what appears on a webpage and they wouldn't be able to show you relevant websites when you search for things.

Most web crawlers, including the ones used by major search engines, respect whenever a webpage tells the bot that it does not want to be indexed to appear in search results. You can actually control this for your own FA pages (like your main userpage and all your submission pages) on the Site Settings page, under the option "Disable Search Engine Indexing".

Aimbot
A program that allows players to cheat in shooter games by aiming the player's weapon automatically. This one is a little bit of a misnomer, since "aimbots" are nowhere near as autonomous as people usually mean when they say "bot". It's basically a program you run alongside the game to help you cheat.

You are getting very technical replies.

In short, a bot is a (normally) small program dedicated to run a very specific task. It has sort of a negative connotation, as they are normally meant to do something a human would have to do manually. Normally they are used to automate a task, or gain an advantage over someone.

That's why you see Captchas all over the place to "verify you are a human".