To perform and portray a character from a true or fictional story intended to entertain a wider audience. This can be dramatic or comedic via any medium including radio, television, theatre, film and street theatre.
Most actors have varying comprehension of what "acting" is and approach the craft depending on their training and experience in performance and life.
For some, acting is life, acting is entertainment, acting is escaping your own personality, acting is a chance to extend yourself in a way that virtually has no limits because you never judge the character in which you play, but research and delve deeply into their world all while naturally bringing your own flavour to the final product.
Acting is not a look darling, it's a skill. Don't audition for me until you get some fucking training.