Parsha Behar is often combined into a double parsha with parsha Bechukosai, which we read next week, but this year we are reading parsha Behar alone.
The first aliyah discusses the Sabbatical year (also called Shmittah year) and the Yovel (Jubilee) year. For the Sabbatical year, we work our land (in Israel) for six years, but the seventh year is a Sabbath for the land. We don't sow the land, harvest it, or prune it. There are many laws governing what can be done and what cannot and what to do with the fruit that grows by itself and how to be a consumer of produce in such a year. Even outside of the land of Israel we need to be careful about produce and canned goods produced in the land of Israel during a Shmittah year.
After seven sets of seven years we proclaim a Jubilee year with a blast of the shofar on Yom Kippur. In such a year all slaves are freed, and all land reverts to its former owner.
The second aliyah says that if we sell to our neighbor, or buy from our neighbor we should not wrong one another. Rashi interprets this buying and selling from a neighbor to mean that when we sell, we should sell to a Jew and when we buy, we should buy from a Jew. Also, we are warned here to take into account how many years are left until the Jubilee year when we buy or sell land, because the land will return to its former owner then. The end of the aliyah states that if we observe and do G-d's statues and ordinances we shall dwell in the land safely.
The third aliyah continues the promise of G-d begun in the previous aliyah that if we observe the mitzvahs we will dwell in the land of Israel in safety. This aliyah adds that the land will produce its fruit to our satisfaction, and adds again that we will dwell in safety. It then promises that we need not worry about what we will eat during the Shmittah year when we can't farm, for the sixth year will produce enough for three years (the sixth, seventh, and eighth years).
The fourth aliyah goes on to give some details of the selling of land until the Jubilee year. One shouldn't even sell his land unless he is poor. When selling one's land, the seller should at least retain a field of it, and a relative of the seller, or the seller himself if his wealth returns to him, may redeem the land from the buyer for an equitable amount and the buyer cannot prevent it.
The fifth aliyah has additional laws of selling real estate with respect to the Jubilee year. Here, the Torah discusses houses in walled cities (like Yirushalayim) which can be redeemed by their sellers for up to a year after the sale, and if not redeemed in that year, become the permanent property of the buyer, and they are not released by the Jubilee. An exception to this is when a member of the tribe of the Levites sells his house in one of the cities of the Levites, the Levite shall always have the power to redeem it, and it will be redeemed by the Jubilee.
This aliyah then turns to the matter of helping one another; we are told that when one of our brethren becomes impoverished, we must come to his aid. And this is where we are told that a Jewish lender may not charge interest to a Jew. In fact, the Jewish borrower is independently forbidden to pay interest to a Jew. (For business purposes, there is a mechanism called Heter Iska - "permission to business", which both partners sign, and permits certain transactions.)
The sixth aliyah states the law of the Jewish bondsman who, because of his poverty, sells himself to us. In short, we are not permitted to treat him with rigor as with slaves, but on the contrary, we are to treat him as a hired servant doing reasonable and necessary work for us, and they are to be released in the Jubilee year.
The seventh aliyah describes the laws of a non-Jew who becomes rich. Rashi interprets: by clinging to you. Also here is the law of a Jew becoming poor which Rashi interprets: by clinging to the non-Jew and learning from his doings. The aliyah continues: the Jew sells himself to the non-Jew, his relatives may redeem the Jew and the Jubilee year releases him.
The Torah then mentions the prohibition of not making an idol. Rashi says this is mentioned here, so that a Jew who is a bondsman of a non-Jew shouldn't forget who he is, and despite who his master is, he still must keep the Sabbath, not worship idols, etc.