Asexual reproduction is where an organism produces offspring which is genetically identical to itself, without fertilisation happening
The main identifying feature of asexual reproduction is that there is only one parent, it is essentially making a clone of itself. This clone is made by mitosis, rather than the normal way of producing offspring - meiosis. The offspring being made by mitosis means that all of the genetic information has come from one parent, and it is not mixed in any way, like it would be in meiosis and sexual reproduction.