Starting from the right--> 3/8ips thru 5/16-27 is hollow, the rest are solid.
The number following the -(dash) is how many threads per inch. So 1/4-27 would have 27 threads per inch.
We generally leave off the pitch on 1/8 thread, it is 1/8-27.
The (finial) threads on the top of a harp are 1/4-27.
1/4-20 is the most popular furniture thread, it is more course.
Unlike plumbing, lamp parts are not tapered (not NPT). Lamp thread IPS is straight or parallel threads, equals the same as NPS National Pipe Straight threads.
Slip is with no threads at all.
Taps make female threads, dies make male threads.
A reducer allows you to reduce the size of a female thread. A nozzle allows you to reduce the size of a male thread.
Females are innies (the threads are on the inside), Males are outies (the threads are on the outside).
Righty tighty, lefty loosey.
"" = inch, ' = foot.
ID = internal diameter , OD = outside diameter