Orthodoxy is perhaps the only Christian denomination in which icon veneration is very developed. Moreover, while Catholics respect sacred images, numerous Protestant churches unanimously accuse the Orthodox of almost idolatry.
In fact, an icon for a believer is not an idol at all, but a reminder of another world, of saints and God. The phrase "bow to the icon" has a slightly different meaning than "bow to God." The icon can be compared with a photograph of a loved one, which is carefully stored in a family album or hung on a wall. No one considers the photo an idol or a replacement for the original, even if much attention is paid to it.
In many religions, there are no icons, and any images are forbidden for a very reasonable reason: no one has ever seen God, so how can the unthinkable be depicted?
Orthodox icon painters also invent nothing, and, according to the rules, icons depict only what was material.
But what about the icon of the Holy Trinity, because no one has ever seen God! This is not entirely true. We saw our God in human form. Jesus Christ is God and man. So at least the second Person of the Holy Trinity can be portrayed. He had some incarnation and the Holy Spirit. He appeared several times in the form of a white dove. It was not a real pigeon, of course, but He can be written in this form.
So, the two Persons of the Trinity are portrayable, but God the Father is not enough for completeness. Icon "Holy Trinity" without the Father can not be.
Icon painters found several ways out of this situation - more or less successful. For example, there is an icon of the Holy Trinity, a photo or a reproduction of which is located in every prayer corner. On it, God the Son sits on the throne, God is the Holy Spirit above Him, and God the Father is indicated by a certain sign of outpouring grace. There is another option, which is usually called Catholic, where God the Father is depicted arbitrarily - an old man, and God the Holy Spirit - a dove. Everyone recognizes that the icon is non-canonical, that is, it does not comply with the Orthodox rules of icon painting, but it was widely used in the 19th century.
The most famous icon of the Holy Trinity was painted by Rublev.
Here is a moment from Old Testament history when three angels came to Abraham. According to the interpretation of the
holy fathers, it was God, and maybe Andrei Rublev used only the image. In any case, the icon is a unique work of not only icon painting, but also theological thought. The Rublev’s Holy Trinity icon is not only that moment at the tent of Abraham, but also eternal advice. This thought suggests the contents of the bowl on the table. In it (according to many interpreters) is the sacrament, that is, the Blood of Jesus Christ. This is a moment of a certain prophecy about the future, about the incarnation of the Son of God and about His suffering. It is this mysterious meeting that is called the eternal advice.
The icon of the Holy Trinity is mysterious, it has a huge number of symbolic details, by which it can be determined that Andrei Rublev each Angel designated a specific Person of the Holy Trinity. Discussions about her are still ongoing. This image is now stored in the church at the Tretyakov Gallery. Here he is under guard, but you can kiss him, pray to God and light a candle.