[Radio Wrangler]

There are real differences, some are subtle.

A 'signal generator' is all-encompassing and therefore almost meaningless unless you know the context it was written/spoken in.

A function generator is usually found in a general purpose electronics lab. Their super power is that they can make various waveforms. Sine, square, triangular, ramps up and down and maybe some pulses. These things are relatively low in frequency, so not good for radio work. Their sinewave distortion is poor because of the way it is formed by distorting a triangle, so they're not good for audio work beyond finding gross faults. There are fancy digital versions where you create ANY waveform as a file and it 'plays' it. These are called arbitrary waveform generators. All of these are usually fairly noisy and impure on their output.

RF sig gens make sines only and cover the tuning ranges of various radios. Expect the facility to put AM on it and perhaps FM as well as a basic audio output. Good ones can go to very low levels... less than a microvolt.

Then there are 'Frequency Synthesisers' machines for making accurate and stable frequencies. They may lack modulation facilities, they may lack good attenuators. With them, they are modern RF sig gens.

Pulse generators do what they say on the can. Usually they go a lot faster than func gens can.

Not all RF sig gens cover all frequency ranges used by radios.

You can do a lot of fixing without one. But having one can make it easier and can make learning easier.

David