first, all modes are scales.
second, not all scales are modes and in that have even have one mode (whole-tone scale has no modes)
third, There is Five proper 7-note scales in 12-tone equal temperament. Meaning, here at lest, that they all have modes and are their own "set" so to speak. They are Diatonic Major, Melodic minor, Harmonic minor, Harmonic major, and Major Locrian. (there are other scales which have as many notes as modes, but they are not notable in western music, besides double harmonic [at lest in modern music, I have yet to see someone use a mode of that scale through], not that some of these scales are used that often [Major Locrian])
That being, only worry about Diatonic Major, don't go on until you fully understand this scale and all it modes.
Diatonic Major
Ionian - 1,2,3,4,5,6,7
Dorian - 1,2,b3,4,5,6,b7
Phygrian - 1,b2,b3,4,5,b6,b7
Lydian - 1,2,3,#4,5,6,7
Mixoldyin - 1,2,3,4,5,6,b7
Aeolian - 1,2,b3,4,5,b6,b7
Locrian - 1,b2,b3,4,b5,b6,b7
so to answer you question...
as stated above the step/intervals of the two scales are different thus making them Different scales. yet when you have C Ionian the 1 is C, the 2 is D, the 3 is E and so on. Then when you have D Dorian the 1 is D, the 2 is E, the b3 is f, and so on.
what you get is.....
ChicagoMedic says:
C Ionian= C D E F G A B C
D Dorian= D E F G A B C D
as you can see they share the same notes/tones therefore they are modes of each other.
maybe you can think of modes like a transformer, when you have a set amount of parts and you can transformer them into car mode or fighting mode and such. Just drop the transforming part and keep in mind the the modes are a set and are intimately contented you got modes and scales.
also I can no more strongly recommend what medic said here
ChicagoMedic says:
Now, playing "modally" involves stressing the root note of the mode (in the case of D Dorian, that is D)
A cool way i do it is to pedal the low E string and play the e phrygian mode....gives a nice flavor
however I add, do the base pedal in different keys and modes. I find the best method to "get" a mode and modes in general is this approach.