Dilruba = stringed instrument that looks like a smaller version of the Sitar, but is played with a bow like a Cello. Another appropriate description is "a Dilruba is Half a Sarangi and Half a Sitar", as you can see from the videos above.
Esraj = Same as a Dilruba, except the bottom is shaped differently. There are a few other small differences also: like the position of the main playing string, and the way the resonating strings are arranged behind the playing string.
Tar-Shehnai = Esraj + Sound Box that produces a high pitched Shehnai type sound.
I've been learning the Tar-Shehnai / Esraj for 3 years. Still need lots of practise, but I'm having fun- and this site is to post up random Tunes i've Learned / Heard.