Well I am far from "expert guidance" but I can tell you a few of the obvious ones...
/var is where logs are kept, amongst other things, but as a rule of thumb, this is the log directory.
/bin is the BINARY directory, this is where executable programs that you install are kept, and scripts as well.
/mnt, well this one would be where you send everything to be mounted that isn't part of the native filesystem, ie CDROM's and such
/boot is where all the bootup information is kept like your kernel and such
/etc is where configuration files for your system are kept
/home is the home directory of normal users
/dev is where BLOCK DEVICES are located, this would most of your hardware
Those are vague answers, and not thought to be complete, but gives you a general idea anyway.
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