First of all, a chorus creates an exact copy of the signal. Subsequently one of these signals is, similar to a delay, reproduced delayed. But the delays of the sound are so short that they are not perceived as delays. They only last 2 up to 70 ms. Afterwards the delayed signal will be modulated. That means that the delay of the signal varies between 40 and 50 ms. This creates an acoustic chorus-effect. The longer the delay-time and the bigger the width of the modulation, the more intense the effect.
The first chorus-pedal was the Boss CE-1. This effect-unit previously has been installed into the Roland Jazzchorus amplifier and has also been offered in a separate enclosure in the late 70th. Still today the sound of the CE-1 is legendary.
Another early chorus-pedal was the Small Clone by Electro Harmonix.
Technically the vibrato is working similar to a chorus. But the original signal is not reproduced. By reproducing only the modulated signal, an intensive vibrato-effect is created.
With the above mentioned Boss CE-1 the guitarists were able to create the first vibrato-effects. Before, this only was possible by using a unit installed to an amlipfier.
The flanger delays and modulates the signal just like a chorus does. But in this case, the times of delay are pretty short (0,5 -16 ms). And some flangers lead back a part of the signal to the input of the pedal to modulate it a second time. The proportion of the lead-back signal can be controlled by the “Feedback”- pot.
A phaser treats the signal in a different way. It shifts the phase of the signal. The shifted phase is modulated at the same time. This causes extinctions in several frequencies. By modulating the shifted phase the frequencies of the extinction varies.
The most famous phaser is the MXR Phase 90.
The Uni-Vibe became famous through Jimi Hendrix. Primarily it should create the doubler-effect of a Leslie-Speaker. But most of the uni-vibe-pedals actually are some kind of phaser- or chorus/vibrato- pedals.
The first uni-vibe-pedal has been developed by Shin-ei. Many of the recent ones are based on this original.
The tremolo is created by a variation of the volume of the signal. This effect can be created almost simple. This is why it has been one of the first pedals, respectively one of the first effects integrated into an amplifier.
One of the first tremolo-pedals has been developed by DeArmond. Inside of this pedal the volume-pot could has been controlled mechanically by a small motor.
A delay creates, just like a chorus, a copy of the original-signal and reproduces it delayed. The times of this delays are much longer and can be heard clearly. Most of the delay-pedals have a delay-time of 30 -600 ms. Some digital delays are able to create delay-times that last up to several seconds.
Frequently the delayed signal can be additionally modulated. This creates floating delay-sounds.
The first delays have been produced by Boss (DM-1), MXR 118 and DOD. Their delay-times were pretty short and they produced besides noise. Later digital delays like the Boss DD-2 created a cleaner sound.
And to those who would like to deepen this issue, I would like to recommend ZING Instruments.