Ahavah means "love" in Hebrew. The Jewish mystics remark on the affinity between the word ahavah, "love," and "echad," one. The numerical value of their letters is the same: 13.
Oneness, unity, is the aspiration of love, and love emerges from a perception of unity. This insight is also expressed in the Shema: its first line declares God's unity, and ends with the word "echad." Then follows the mitzvah to love God. Love comes out of a sense of God's unity pervading all things.
There are three commands to love in the Torah; "love your neighbour as yourself"(Leviticus 19:18); "love the stranger as yourself" (Leviticus 19:34); and "You shall love the Lord your God for all your heart, soul and strength" (Deuteronomy 6:4).
The commentators are exercised by the question of how we can be commanded to feel an emotion such as love. Surely we either have it or we don't. The general answer is that, indeed, one cannot command feelings. The content of these mitzvot to love is that one performs actions which will engender love.
In the case of love of God, the point is to open oneself up to the awe and amazement of God's creation. In the case of love for other people, the Torah is telling us to act lovingly; to go visit the person in hospital, give charity, take out the rubbish, or change the baby's nappy, and that this will bring us to love