5 Hosea 4 v 6 My people are destroyed for lack of knowledge: because thou hast
Here are some links to use if you have a smartphone and want to get a helpful app:
There is a text by Alexei Khomiakov, amounting in length to a little booklet translated into English from Russian in the 1800s which is still standing as a concise and true summary of Orthodoxy suitable for all of us to read and internalize. It would satisfy at least the adult portion of the wikipedia definition of a catechism (below) and can be found by clicking here.
“A catechism is a summary or exposition of doctrine and serves as a learning introduction to the Sacraments traditionally used in catechesis, or Christian religious teaching of children and adult converts”. (Wikipedia definition). It aims to provide a solid and sound foundation for growth in faith and holiness within the ancient body of the Holy Church.
Another trusted source of Catechism to turn to has been provided for us by St Philaret of Moscow (icon on the left) and can be found online when clicking on: The Catechism of St Philaret (Drozdov) of Moscow
Another, more recent Catechism, also online, is a pdf document of 55 pages inspired by THE MYSTERY OF FAITH: An Introduction to Orthodox Dogma and Spirituality, by Hieromonk Hilarion Alfeyev and can be opened by clicking on this link: http://www.stseraphimmichigan.org/big/catechism.pdf