A legislature is the lawmaking body of a province or state. Some have also historically been courts of justice, whether serving exclusively in that role, such as the pre-Revolutionary Parlement of Paris, whose sole legislative function, beyond administering justice, was to register royal decrees.
Legislatures may have one (unicameral) or more chambers (bicameral, tricameral, etc). The head of government, or even the head of state, may also be an essential part of the legislature.
Some English terms for a legislature include Parliament (used in parliamentary systems), Congress (used in congressional systems) and Diet (German, -tag as in Bundestag), as well as Soviet, Storting, Althing among others.