Internet Download Managers (IDM for short and non-mouthload) are softwares that help you download things by managing and scheduling downloads (and in some cases making them faster).
They were mostly used in the past before browsers integrated most of those options aswell, and usually that's the only thing the day-to-day user needs.

However, I did not go to the full extent of what these capable little bastards can do. They can help you by letting you choose how much bandwith a download can occupy, speed up downloads, the option to download videos and their playlists (although not in high-quality of course), download multiple files at once, and the option to recover and resume downloads in case something happens, like network interruption, sudden powerdown, etc.

All of these traits are shared by torrent clients, yes. But they're for day-to day downloads and not every website offers the option to download torrents (looking at you, games in FitgirlRepacks!) and are useful for people who need to download big files/multiple files a day or who have bad internet connection (like me!)
Honestly, the only cons are mostly ones that already come with downloading things in general like:

*Files that may be infected with malicious agents, such as trojans or viruses. Some IDMs offer you the option to analyze the files for threats, but personally I just check that with Virustotal before downloading if it's like a setup (program that is small in file size and once you run it it actually downloads the stuff you need), or simply Windows Defender will do.

*Privacy risks, since you are using a third-party for your files, so read up on what IDM you use.

*The file (the IDM) may be infected and could affect your computer and you may get malware/spyware or something -ware. This risk already comes with downloading files in general even if you don't use an IDM, and to be honest if you have your system up-to-date you'll get an alarm before or after downloading the file, if not from the browser itself. So long as you read up on this you should be fine.




And you might be thinking "but what about websites that have human-captchas? Or that need an account to download?" and fear not! these problems have already been thought of previously, and people have made it so that IDMs can bypass the captchas (or most of them) and have options for you to insert your account and use it for the downloads. Of course, it has a safety risk, like I said earlier with the privacy one. But honestly so long as you read up on your IDM and see reviews I think you'll probably be fine. If not, I'm so sorry.

An IDM I can recommend is JDownloader. I can't exactly put my hands in the fire for it, but it's compatible with Windows, Linux, and Mac OS. It's open-source (which basically means its code is peer-reviewed by anyone in the world since it's public), and it's free. I've used it and it downloaded videos in decent quality (and even gave me the option to download subtitles, audio and video track separately, and the thumbnail) and made a download where if I used my browser it would've taken 2 hours, roughly, and it downloaded it in less than 30 minutes, wow.