The Institutional Architecture

The Eur-Lex website contains links to the texts of the treaties of the EU.
http://eur-lex.europa.eu/collection/eu-law/treaties.html

The European Union's page on institutional affairs contains an overview of the EU’s institutional architecture and information on EU legislation on institutional affairs.
https://ec.europa.eu/info/policies/institutional-affairs_en

The Europa website provides a comprehensive overview of the EU budgetary procedure (click on the links across the top of the page for further information).
http://ec.europa.eu/budget/budget_glance/index_en.htm

The Europa website also provides a detailed overview of the EU’s decision-making procedures.
https://europa.eu/european-union/eu-law/decision-making/procedures_en