One of the meanings of the name of the month 'Adar', can be explained by dividing the name Adar into two parts: the letter 'Aleph' and the words "Dar". The letter Aleph alludes to G-d, the One and only, the Master of the world (אלופו של עולם). The word "Dar" in Hebrew, means 'dwells'. Now we can understand the characteristics of this special month Adar. It is a month where our ability of achieving the goal of having G-d dwell within the Jewish nation as a whole, as well as within each and every one of us, is immense.
One essential tool that enables us to reach the desired state of having G-d live within us, is Simha (happiness). We are all familiar with the famous phrase from the Gemara, "Mishenikhnas Adar, Marbin BeSimha" (when Adar comes, we increase our happiness). Our Rabbis of blessed memory teach us that the Shekhinah (G-d's holy presence), cannot rest upon a person who is not happy. In simple words, sadness pushes away the Shekhinah.
We can see that the fact that the month of Adar is characterized by an increased level of happiness, lends itself to achieving "Adar", i.e., bringing the Master of the world to dwell right inside each and every Jewish person.