This number, what does it mean? Our universe resonates with the number 12. Source created the "central sun" of our present universe, which is a heavely body, black hole or star, depending on from which dimension you look at it. Two beings from another universe came to become the consciousness of that star, a male being and a female being (the latter incarnated as Maria, Yeshua's mother). They created 12 energy beings called the "Rays", because they each represent certain frequencies and as such the qualities of Prime Creator. From the Rays came 12 soul families of 12 (= 144), the 12 Tribes of Creation. They constitute the groups of Archangels, Elohim and the so called Lords of Light and Co-creator Council of Twelve. These folks went on to create our universe, together with the Universal Father and Mother.
On the micro scale the number 144,000 represents the number of Nadis (energy channels) in our bodies during Kundalini activation (you may look elsewhere for more precise information).
Of particular significance during Ascension are the 144,000 people on Earth that reach a certain frequency (representing their level of consciousness). Then the Ascension process will have critical mass, but of course Ascension will not be limited to 144,000 people, it's just the beginning.