okay. let me explain this in the simplest way I can.
sis, ano ba ang pagkakaintindi mo or ang turo sayo pagdating sa mga idolo? diba ang idolo ay isang bagay na kung saan mas binibigyan naten ng halaga kesa sa tunay na Diyos?
so, ang concept or konsepto ng idolo, hindi po sya limited sa mga bagay na gawa sa kahoy or sa mga rebulto.
idolatry is made up of two greek words Idolo + Latreia, which means the worship (lateria) of any image or object. (idolo)
going by this definition then, a person can become idolatrous even if he or she is not worshipping any statue.
and so, the concept of "Idolatry" goes beyond wooden carvings. most importantly, the
concept of "Idolatry" finds a deeper meaning in morality. simply put, maski Born Again ako, or Muslim, or Iglesia pero iba ang sinasamba ko maliban sa iisang Diyos, i can fall into the sin of idolatry even without believing in statues or saints.

pwede ko maging diyos ang pera, or ang sex, or ang alak. they are not necessarily statues pero pagka itong mga bagay na ito ay nakakasagabal sa pag samba ko sa Iisang Diyos, idolatry na yun.
on the other hand, pagka ang mga istatwa or rebulto or paintings ay nakakatulong para mas mapalapit ako sa Diyos, hindi sya Idolatry, kase the purpose is to make me closer to God.

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now, maybe you'll ask "bakit pa may mga istatwa ang mga katoliko, hindi ba wala naman sa bibliya yan"?
sasagutin ko ito:
basically, a statue or any image is a sign, or symbol that points to something other than itself.
noong unang panahon, maraming tao ang hindi pa marunong mag basa o magsulat, especially during the time of the early Church. but of course, hindi porque hindi marunong mag basa or mag sulat ang tao, eh ibig sabhin wala na syang karapatan para malaman ang Salita ng Diyos
the solution was to paint or to depict in artistic forms certain stories in the bible or Gospel scenes so that those who cannot read or right can still appreciate the message of the Gospel.
so, for example, this painting by Michelangelo
http://www.cs.utah.edu/~bigler/pictures/europe2002/italy/sistine%20chapel.jpgdepicts certain scenes in the book of Genesis to show the fall of Man from the love of God
or this statue by Giancarlo Bernini
http://www2.kenyon.edu/Depts/Religion/Fac/Adler/Reln482/Images482/Bernini-Teresa.jpgdepicts the "ecstasy" of Saint Terese of Avila.
the beauty of these images is that they are primarily "signs" that point to a greater reality, which is the Gospel.
is my explanation fair enough?

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by the way, yung mga painting at statue na nakita mo, they are found in the Vatican City, inside the City of Rome.
The Vatican City is a State, and is also at the same time the Head Quarters of the Roman Catholic Church
http://lh4.ggpht.com/fisherwy/R9aQFqLXUgI/AAAAAAAAN2I/2_STgvY3PF8/vatican+city[2]