The Christmas Tree Cluster also known as NGC 2264 is located in the constellation Monocerus. In fact, it is not clear whether NGC 2264 also refers to the Cone Nebula. According to the SEDS database, NGC 2264 is a "Cluster associated with nebulosity". The cluster is located approximately 2'300 light years from Earth.

The Cone Nebula is an HII region and was given the designation H V.27 by William Herschel. It is located approximately 2'700 light years away from us.

Also in the image is Hubble's Variable Nebula or NGC 2261. The nebula shines due to the star R Mon. The main star of this binary star system is variable and causes the brightness of the diffuse nebula to change.

Image on Astrobin: https://www.astrobin.com/0mgr30/
Image on Instagram: https://www.instagram.com/p/C3ONjL4Mjdd/?hl=de&img_index=1

Timelapse of Hubble's Variable Nebula: https://www.youtube.com/watch?v=cdW-ptTo4FM

Sources: 
https://en.wikipedia.org/wiki/NGC_2264#cite_note-cseligman-7
https://spider.seds.org/ngc/ngc.cgi?NGC+2264
https://en.wikipedia.org/wiki/Cone_Nebula
https://en.wikipedia.org/wiki/NGC_2261
https://en.wikipedia.org/wiki/R_Monocerotis