This is the 8617th most frequent Russian word.
орла
"Орла" means "eagle" in English.
In this sentence, 'орла' is the accusative case of the masculine noun 'орел' (eagle), indicating the direct object receiving the action of being seen.
На верхушке дерева я заметил орла.
I saw an eagle at the top of the tree.
Here, 'орла' is used as the genitive case of 'орел' to specify 'the image of the eagle' as a part of the description.
Мы изучали картинку с изображением орла.
We studied a picture with the image of an eagle.
In this example, 'орла' is in the genitive case of 'орел,' explaining possession or relation—'a statue of the eagle'.