3 of the most basic parameters of delay are
1) Mix
2) Repeats
3) delay time
For 1), some different brand delay use blend, effect level, etc to call it. What it does is as what the name is, to vary the "delay effect" in relation to your main signal, according the the setting of this parameter
Its like a percentage divider, to divide how much your instrument signal get to be delayed and mix with your original signal
For 2), some other maker might use intensity, effect level etc to call it. Its basically for you to vary the amout of repeat for your delay effect.
As you shud already know or have heard, a delay effect caused a repeat of what your play on the instrument. For example, when you play a note, lets call it "A". Delay effect will processed this "A" note and make it ring out in repeatitive "A" note, till it fade.
With this parameter you can vary your "A" note to have it in having only 1 repeat or continous repeat of it, according to where you set it.
For extra info, this repeat control can give an effect call "self oscillation"(anyone who uses delay for textural content most prolly will know this/must know this). As you set your repeat to maximum, this delay effect will start to get louder and more out of control, due to the delayed signal, feeding back to the input and getting more delayed, over and over again.
Some delay cant get this thou, basically with repeats at maximum, your signal just keep going on and on without getting back to the input.
For 3), some maker use rate to call it. Its for setting the "time interval" of your "delay signal" .
basically, setting this time will set a fixed interval between the note you played and its repeated notes.
For example, lets play the same note again, "A"
When its being processed by the delay and having repeats at 3x, you will hear the following
A-----A-----A-----A
Biggest A is the note you play, smaller A are repeated notes. Time/rate is the ----- in between notes. Its for you to set how long/short between the repeated notes.
When you adjust time/rate, you will see/hear the following
A----------A----------A----------A
or
A---A---A---A