As an Android nerd, there are times you probably need ADB or fastboot to mess around with your phone. Maybe you're flashing an OTA or unlocking the bootloader. You used to need to grab a giant package of other junk from Google to get them, but no more! Google has started hosting platform tools downloads without the other stuff that are a mere 3.5MB.
You can get the platform tools for Windows, Linux, or Mac direct from Google's servers. You get a ZIP file containing the platform tools folder with ADB, fastboot, and a few other tools. Previously, you'd have to download Android Studio or the SDK to get these, which are a 400MB-1.6GB download. Even the smaller command line tools download is still 200-300MB. If you're not doing development work, you don't need all that junk.
There are some third-parties that host files like ADB and fastboot, but then you have to wonder if the files are out of date or malicious in some way. It's much safer to get the tools from Google, and now it's easier too. These downloads should be kept up to date going forward, so have fun.
- +Elliott Hughes