On the Shabbat preceding Purim, which is this coming Shabbat, after the opening of the Ark immediately following Shacharit prayers, two Sifrei Torah are removed; in the first one, we read the weekly Parasha (which is Parashat Tetzaveh this year, 5778) and in the second one we read the portion of “Zachor Et Asher Asa Lecha Amalek” (“Remember what Amalek has done to you”). This Torah portion is referred to as “Parashat Zachor”. (Parashat Zachor can be found at the end of Parashat Ki Tetzeh in the Book of Devarim.)
According to most Poskim, the reading of Parashat Zachor is a Torah obligation. Since the Halacha is well-known that “Mitzvot require intention” (Shulchan Aruch, Chapter 60, Section 4), one must take care while listening to Parashat Zachor to have in mind to fulfill the Torah obligation of remembering the actions of Amalek and obligation to annihilate them. Similarly, the individual reading from the Torah must have in mind that the entire congregation will be fulfilling their obligation by listening to his reading.
One who, due to pressing circumstances, could not hear the reading of Parashat Zachor on this particular Shabbat should have in mind to fulfill his obligation the next time this portion is read, which is on the Shabbat of Parashat Ki Tetzeh. In this situation, one must ask the person reading the Torah to have him in mind while reading so that he may fulfill his obligation. Maran Rabbeinu Ovadia Yosef zt”l writes that nevertheless, one should preferably read Parashat Zachor from a Chumash on Shabbat Zachor.
There is a dispute among the Poskim whether or not women are obligated to hear the reading of Parashat Zachor. The Sefer Ha’Chinuch and others maintain that women are exempt from hearing Parashat Zachor since the underlying reason for reading this portion is to remember the actions of Amalek in order to wage war against them and women do not usually take part in active combat nor are they commanded in the Mitzvah of fighting; therefore, they are not obligated to hear the reading of Parashat Zachor. (Clearly, there is no distinction between an average woman and a woman of uplifted spirit who would like to go out to war, for the Torah does not command women to annihilate Amalek since women do not usually take part in conquest.) However, many Poskim are of the opinion that women are obligated to hear Parashat Zachor (which is indeed the prevalent custom). Thus, those women who act stringently and attend synagogue to hear Parashat Zachor are indeed praiseworthy. A woman who has small children and cannot leave them to hear Parashat Zachor may exempt herself from hearing Parashat Zachor.
Nowadays, it is customary in many places to take out a Sefer Torah and read Parashat Zachor especially for women after morning prayers have concluded; in this way, women will indeed be able to hear Parashat Zachor while someone else attends to the children at home. This should preferably be done at a time when there are ten adult men present in the synagogue, such as shortly before Mincha services. This is indeed a fine custom.