Eurasian Tree Sparrows look similar to House Sparrows.
If you want to tell them apart, remember that Eurasian Tree Sparrows have a brown cap and House Sparrows have a grey cap.
Male and female House Sparrows look different while male and female Eurasian Tree Sparrows look similar.
In Europe you may find this bird in wooded open countryside, while the similar looking House Sparrow breeds in the more urban areas.

Lake Kerkini, Greece, 16 April 2016