Wikipedia
Yesha is a Hebrew acronym for " Judea, Samaria, Gaza" (, "Yehuda Shomron 'Azza") - a geographical area, roughly corresponding to the West Bank and Gaza Strip combined. Yesha is one of a number of terms used to describe the areas of former Mandatory Palestine, occupied by Egypt and Jordan and later became a part of a military governorate.
The Israeli Military Governorate was established by Israel in the Israeli-occupied territories following the Six-Day War in June 1967, together with Sinai and Golan areas. In 1982, areas of Yesha were transferred from military occupation governance to Israeli Civil Administration under the Ministry of Defense, whereas East Jerusalem was unilaterally annexed to Israel; the same year Sinai was returned to Egypt, while Western Golan unilaterally annexed via the Golan Law. In 1994 and 1995, much of Yesha was transferred to autonomous rule of Palestinian Authority, under the Oslo Accords.
Israel disengaged from the Gaza Strip in 2005, thus emptying the political meaning of Yesha on behalf of Israel. Other acronyms used by Israelis for the West Bank portion are Shai (ש"י Shomron VeYehuda - Samaria and Judea), and Ayosh (איו"ש Ezor Yehuda VeShomron - Judea and Samaria Area).
The Yesha Council is the umbrella organization of the various municipal councils (local, regional, and cities) which represent Jews in the area. The Judea and Samaria area administrative division was established to govern Israeli communities within the boundaries of Yesha (in area C of the West Bank).