The Electoral System in Israel
Israel has an electoral system based on nation-wide proportional representation, and the number of seats which every list receives in the Knesset is proportional to the number of voters who voted for it. The only limitation is the 2% qualifying threshold. In other words, a party must receive at least 2% of the votes in order to be elected. According to this system, the voters vote for a party list, and not for a particular person on the list. Since the institution of the primaries system in some of the parties, these parties directly elect their candidates for the Knesset. Some of the parties elect their candidates via the party's institutions. In the ultra-religious parties their spiritual leaders appoint the candidates. The Knesset elections take place once every four years, but the Knesset or the Prime Minister can decide to hold early elections, and under certain circumstances can serve for more than four years.The Principles Upon Which the Electoral System is Based
The principle of the generality of the elections ensures the active right of every Israeli citizen, who is at least 18 years old, to vote and the right of every Israeli citizen, who is at least 21 years old, to be elected. Even though the Basic Law: The Knesset gave the legislator the power to deny the right to vote to anyone as it may see fit, the Knesset has never made use of this power. Those holding certain official 
positions, such as the President, the State Comptroller, judges or dayanim, career officers, and senior civil servants, may not stand for election to the Knesset. However they can contend if they resign from their post 100 days or 6 months before the elections, depending on the public position, as the law specifies.
The principle of country-wide elections states that Israel is a single electoral district insofar as the distribution of Knesset seats is concerned. Direct elections mean that the voter elects the Knesset directly, rather than an electoral college (as is the case in the election of the President in the United States). Equal elections apply to equality amongst the votes given, and theSupreme Court laid down that the principle of equality relates to equality of opportunities for all the lists participating in the elections as well.
The principle of secrecy ensures fairness in the elections and aspires to prevent the placing of effective pressure on voters, since no one has any way of knowing how they actually voted. The principle of proportionality manifests itself in that all the lists, which get past the qualifying threshold, are represented in the Knesset by a number of members which is proportional to their electoral strength.
The Frequency of ElectionsThe Knesset elections are supposed to take place every four years. The Knesset can decide, by an ordinary majority, to dissolve itself and call for early elections. Under the direct vote for Prime Minister system, the Prime Minister could notify the President of early elections. After the abolishment of that system, the Prime Minister can recommend to the President to call for early elections, but the Knesset can block that initiative. The Knesset can also decide, by a special majority, to prolong its term beyond four years. This happened in the case of the elections to the 8 Knesset (1973) which were delayed because of the Yom Kippur War. In either case of delayed or early elections, the newly formed Knesset is meant to serve a full four-year term from the date of elections as determined by the law, regardless of the election date.
Who is Elected to the Knesset? The candidates of any given list are elected to the Knesset on the basis of the order in which they appear on it. If a certain party received sufficient votes for 10 seats, the first 10 candidates on its list will enter the Knesset. If a Knesset member passes away or resigns his seat in the Knesset for whatever reason, the next on the list will replace him/her.
(more information on : knesset.gov.il /// Article bientôt traduit en français)
(Pictures : Knesset from outside and from inside)