In England, the word ceilidh has come to mean a social dance of a more vigorous type than a barn dance...these are usually associated with the style of dance/music that is based in the 50s square dance revival, or the more stately dances of John Playford or the modern dance masters.
e-ceilidh is a specific"movement"...the e standing for english to distinguish it from Scots pr Irish type ceilidhs.
E ceilidh has its own web presence which someone more techy than I may find a link to.
Playing informally in a pub or a house is a session.
Hope that helps...