Ab min7 - Db min - Eb min7 - Gb7
I looked it up and it said it was in the key of B and Ab min? Not very good with theory so I don't know how it could be a major and minor key at the same time.
Thanks in advance.
In addition to Tim's answer, despite the chords being available in both B major and G# minor, this progression is definitely in G# minor (or Ab minor).
When trying to figure out the key of anything, you should look for the tonal center. This means, which note (or chord) gives the sense of conclusion. In this case when you get to the last chord, and loop back to G#m7, it feels like conclusion. If B is not played, it couldn't be the tonal center.
PS: The reason G# minor is preferred over Ab minor is that G# minor has "just" 5 sharps, and Ab minor has 7 flats.
It's better calling the chords G#m7, C#m, D#m and F#7. All of these now fit diatonically into B major. The relative minor to B is G#m, which has the same chords available.
Strangely, there are many guitarists who prefer to talk in sharp keys as opposed to flat keys. Maybe they just are opposed to flat keys...
Every 'key' as in key signature, has a relative major and minor. B major/G# minor has 5# in its key sig.
If you wanted to stick with the flat chords, then it could be said that it's in Abm - or Cb. An unusual but not unknown key to write in...
Please do not believe everything you read on the websites (unless it's this one!) as there is a lot of misinformation out there. Or stuff written in a way that confuses.