Music modes may be conceptually difficult. I'm going to try to simplify them into one paragraph.
A musical mode is allows a musician to utilize a key which altering its root note. For instance, A Aeolian (natural minor) contains the same notes as C Major. Therefore, you are playing C Major notes but with a different tonal center. Thus the music takes on a unique character. If for the same notes your tonal center is C, then you are playing in C Major. By altering the tonal center, you alter the musical character. Another example is E Phrygian, which is also the same notes as C Major. This works because the four accidentals in E Major are flatted in Phrygian.
In summary, modes provide access to additional configurations of notes.
