This portrait of two friends was probably made in late imperial Russia (1910-1917). The only thing written on the back is a pair of names, which look to me like Tyosha and Marusya (Tеща и Маруся). I’m not sure about the name Tyosha, as I haven’t encountered it before:
The girls are both dressed entirely in white. Was that for school graduation? They look to be in their late teens, maybe 16-18 years old. (I have a hard time guessing ages!)
The backdrop is skillfully painted yet understated, with a single birch tree suggesting the vast boreal forest which covers most of Russia to this day.