The thing to realize about modes is that they are simply emphasizing different key notes in the same collection of notes.
Take a scale, any scale, and "emphasize" one note. This will make the "Scale" sound different than if you emphasize a different note.
C ionian and A aeolian are the common major and minor(almost) type of sound. But they are exactly the same notes. What makes them different is that in one you are emphasizing C and in the other you are emphasizing A.
That is, you somehow make the listener lock onto the root note. You do this by setting it up using certain techniques.
For example, if you take CDEFGAB as your "scale" but play a B in the background underneath everything you play, B will seem to dominate(not to be confused with the dominant) the sound. Every note will be heard against that B and your ears will treat B as the "king" of all the notes.
This means if you play a C against it you are playing a min2nd interval. This interval doesn't exist in C major because the 2nd interval is D which gives a maj2nd. The other intervals are just as important and all of them relative to B give that characteristic sound which we call locrian.
Now if you simply changed the root emphasis to A then that C is not a min3rd which gives a minor sound.
For example, if you take a single line solo and play a B bass note it will transform the sound than if you played any other note.
In fact, if you want, you can think of all modes, scales, keys, etc... as simply coming from the chromatic scale and whats makes all the different sounds different is simply emphasis. C major is the emphasis of the note C followed by others less and less so. A min is the exact same 12 notes but we emphasis an A as the root and others less and less.
Effectively we create a hierarchy. You have your king, queen, prince, servants, etc...
The best way to really hear it is to simply play the same scale over a minor chord and then a major chord and hear how it changes.
Note that it is possible to play sort of major sound over a minor chord by emphasizing that a major sound in your solo. e.g., if you play C E G over a static A bass note you'll have a more major sound than if you play C E A. This is because you are outlining(called an arpeggio) the C major chord even when the bass note is A. Depending on a lot of factors you might hear the A note as being part of the C chord rather than the G being part of the Am chord. i.e., you have the notes A - C E G. But depending on context your brain might group them as A C E - G or A - C E G. The first case we have a sort of Am called Am7 and the second we have a sort of Cmaj6. Most likely you will hear Am7 unless the A bass note is very quite.
In any case it doesn't matter much about the theory as you need to learn the sounds. You just have to know that it all depends on emphasis and context. If I'm playing a Cmaj chord and you're playing a Dbmaj chord at the same time what key are we in(assuming that's all we are playing)? what mode? The answer is that it depends.