The series is based on the film "Nikita", but with strong influence from the English tv series "Callan". The first episode practically retells the film. One difference, presumably to make the leading character more sympathetic to the viewers, is that in the film Nikita was a murderer, whereas in the series she is framed for murder. Section One, the organisation that Nikita is working for, is an anti-terrorist organisation, working similarly to Section in "Callan". People are recruited against their will, and they are treated as expendable if they don't perform efficiently. Nobody ever retires from Section One, they work until they die. In the first season of "La Femme Nikita" there is no doubt that Section One is on the side of the "good guys", but as the series progresses this is put into doubt. The leaders are so ruthless in their fight against terrorism that they are willing to accept any level of collateral damage in order to succeed.
A frequently asked question is where Section One is located. In the film everything takes place in France. It's a French film, after all. In the television series it isn't so clear. Everyone speaks English, and although the series is filmed in Canada I assumed that it takes place in an unnamed town in the north of the USA. This is typical for Canadian series; they are filmed in Canada, but prominent landmarks are avoided to give the impression that the action is taking place somewhere in America. See "Highlander" as an example. This changes in the third season. In the first two episodes we are given a strong clue that Section One is in France, when we see letters showing that Michael's home address is in France. In the 16th episode of the third season we see a prominent landmark for the first time; the Eiffel Tower is visible when the agents leave the building. This is a superimposed image, of course, the episodes are still being filmed in Canada. We can deduce from this that the people in Section One are all speaking French, but through the magic of television we are hearing them in English.