Can someone please tell me the title of this piano piece in this instagram video?
That's The Entertainer by Scott Joplin. It is one of the most famous songs in the "ragtime" style. This was a syncopated piano style adapted from classical music by African-American musicians that was a precursor to the development of jazz, and popular in the mid 1800s. This particular song experienced a renewed burst of popularity after been featured prominently in the 1973 movie The Sting