Sayeret literally means "reconnaissance unit" in the Israel Defense Forces (IDF). In practice, these units specialise in commando and other special forces roles, in addition to reconnaissance (the degree of specialization varies by units and current needs). Such units are usually a company or a battalion in strength.
All combat brigades in the IDF have a unit with improved weaponry and training used for reconnaissance and special forces missions. Historically the brigades used to only have one company-sized unit outfitted to do this job, known as Palsar (Hebrew Contraction of: Plugat Siyur (singular) / Plugot Siyur (plural), "Reconnaissance Company"). Although the Palsar are mostly oriented at battlefield support (which is their raison d'être), many have participated in special operations during recent years. All infantry units as well as some armoured and engineer units have Palsar.
While in the past there were differences between the siyur units, due to the experiences of the past decades the IDF is now consolidating them into larger units with many different capabilities: battalion-sized units called Gadsar (contraction of Gdud siyur, "Reconnaissance battalion"). Each Gadsar is made up of three specialized Plugot (companies): Demolitions (Plugat Heil Handasa, or Palhan), Reconnaissance (Plugat Siyur, Palsar) and Anti-Tank / Heavy Weapons (Plugat Neged Tankim, or Palnat).
This is part of the Yatah ("Low-Intensity Combat Unit") Project. This project aims at changing the Reconnaissance battalions into specialized urban counter terror units, that are specifically trained and equipped to operate in current combat situations.
Other sayarot are larger units, operating under corps and commands. There are several battalion-size special forces units which report directly to regional, functional (navy/air-force) and the general commands. The best known of these are Sayeret Matkal, Shayetet 13 and Sayeret Shaldag.