Seven is a special number in Judaism. Seven are the days of the week (six days of creation + Shabbat). In many Jewish weddings, the partners circle each other seven times. We make seven stops when carrying a casket to the grave. Seven are the colors of the rainbow.
We count the Omer for seven weeks between Pesach and Shavuot, and some of us do a reverse Omer count during the seven weeks between Tisha b'Av and Rosh Hashanah. And all of these sevens can be echoes, or reminders, of the seven energetic qualities that our mystics find in divinity (and in us.)
Our mystics understand God to be both transcendent (infinite, beyond our grasp) and immanent (reachable / relatable / embodied in creation). They envisioned a map of ten divine qualities or energies (called sefirot) through which God's infinity flows into finite creation.
You might imagine the sefirot as electrical transformers that enable the energy of divine infinity to "step down" and modulate to a level that's graspable in physical creation. Sometimes these ten qualities are depicted as nodes in a map of energy-flow. Sometimes they're depicted superimposed over an image of a tree, or over an image of a human being.
At the "top" of the map is Ein Sof -- "Without End," limitlessness, infinity. ("Top" and "bottom" are metaphors for something that's not actually spatial at all, but we use a spatial metaphor to help us imagine this.) The "upper" three sefirot are usually considered so lofty that we can't reach them. (Different schools conceptualize the upper three in different ways and with different names: "Crown" and Wisdom and Understanding, or Wisdom and Understanding and Knowledge.)
But the "lower" seven sefirot are energetic qualities that are accessible to us and are manifest in creation. These are the energetic qualities that we cultivate and discern during the year's two seven-week corridors of inner work and counting: one in the (Northern hemisphere) spring between Pesach and Shavuot, and the other in the (Northern hemisphere) late summer / early fall between Tisha b'Av and Rosh Hashanah. They are chesed, gevurah, tiferet, netzach, hod, yesod, and malchut.
Chesed is love, lovingkindness, unbounded flow. Chesed is the outpouring of overabundant love.
Gevurah is boundaries, strength, judgment. Gevurah is a strong channel, and the ability to discern good from bad.
Tiferet is harmony, balance, beauty. Some see tiferet as the perfect harmony of love and boundaried-strength.
Netzach is endurance and perseverance. Netzach is the energy of persistence, the energy of eternity.
Hod means both humility and splendor. This can be a kind of koan: splendor-in-humility, humility-in-splendor.
Yesod is foundations, roots, generativity. Yesod roots us in the generations, both past and future.
Malchut, sometimes translated as nobility or kingship, is presence and manifestation. Malchut is associated with Shechinah -- the immanent indwelling divine Presence, the divine feminine, the essence of Shabbat.
Each person manifests each of these qualities. One component of the inner work that Jewish tradition calls us to do is discerning which of these qualities we need to strengthen and how to keep them in good balance. Each of these is a good thing when balanced with the others, and each can become a negative thing if it grows unchecked. (For instance, chesed -- lovingkindness -- is a wonderful quality -- but if it flows without limit, it can lead to ethical breaches, boundary crossing, and spiritual bypassing.)
Tisha b'Av is coming up at the end of this week. After Tisha b'Av, there are seven weeks until Rosh Hashanah. During the seven weeks after Pesach (the Omer count) we begin with the quality of chesed and culminate with the quality of malchut. During these coming seven weeks, we begin with malchut -- presence, Shechinah, the divine feminine -- and "ascend" the energetic ladder all the way back to chesed, the energy of lovingkindness that will lead us into the start of a new Jewish year.