Aliyah, the Israeli equivalent of immigraton, is the name given to the legal process of obtaining citizenship and residency by moving to the State of Israel.
Aliyah (rise up) is a process available to Jews worldwide who can prove their Jewish heritage to the Israeli government.
It is one of the fundamental tenets of Zionism, and is encouraged and incentivized by the Israeli government and by organizations such as Nefesh B'Nefesh that help new olim by granting financial aid packages and guidance to ease the assimilation into Israeli culture.
While Jews immigrated at a steady rate to Israel throughout the country's history, there were few notably massive immigration waves over time, bringing in Jews from all over the world.
