SpaceSniffer - SpaceSniffer is a freeWare (donations are welcome) and portable tool application that lets you understand how folders and files are structured on your disks.
PuTTY - Popular free terminal application. Mostly used as an SSH client.
WinDirStat - WinDirStat is a disk usage statistics viewer and cleanup tool, inspired by KDirStat.
MobaXterm - Enhanced terminal for Windows with X11 server, tabbed SSH client, network tools and much more
WizTree - WizTree quickly finds the files and folders using the most space on your hard drive. It scans the MFT (Master File Table) instead of crawling the entire disk which makes it very fast.
iTerm2 - A terminal emulator for macOS that does amazing things.