Conceptual art is art where the concept or idea is more important than the finished piece or how the piece over all looks.
He art movement started in in the 1960s and the name conceptually is given to art made from 1960s – 1970s.

Fountain, 1917/1964
https://d5wt70d4gnm1t.cloudfront.net/media/a-s/articles/1519-393214972123/the-art-book-conceptual-art-900×450.jpg
When an artist uses a conceptual art form it means the planning and decision making are made before think about the aesthetics. The artist needs to think of what message they want their piece to have and what they what people to feel when they look at the piece of art.

An oak tree 1973
https://www.artspace.com/magazine/interviews_features/book_report/turning-water-into-an-oak-tree-michael-craig-martin-discusses-performing-a-miraculous-act-of-55188
Conceptual art can be- and can look like anything. Unlike a painter or sculpture who think of how to show their ideas through painting or plaster. A conceptual artist uses what ever materials best shows their idea.

Sol LeWitt
Red Square, White Letters (1962)
https://d5wt70d4gnm1t.cloudfront.net/media/a-s/articles/2622-179346653886/9-conceptual-artworks-that-you-need-to-know-ORIG.png
Marcel Duchamp is often seen as an important leading figure for conceptual art with his “fountains” in 1917 which is labels the first piece of conceptual art.

Erased de Kooning drawing 1953
http://www.modernedition.com/art-articles/absence-in-art/rauschenberg-de-kooning.jpg
Conceptual art questioned the highly commercialised art, they also question politics in theirs work which makes a lot of the pieces controversial.
Conceptual art challenge what art is, they question who give it the name art and can’t anything be art?