A designer is a person who designs things. Designers plan how something will look.
For example, an architect is a designer of buildings. An architect draws detailed blueprints that show how the structures should look like and how they should be built. The word “designer” came into English in the seventeenth century. It meant "one who schemes." The word then came to describe someone who figures out how something should look.
A graphic designer is the person who planned how the text and images should look on each page of a magazine or a newspaper.
A fashion designer is someone who comes up with a vision for a garment and creates sketches to show what the finished product will look like.
If you want to become a designer, you need certain technical knowledge. You are also expected to have artistic skills.