What is the difference, if any, between a pickle, a chutney, and a relish?

A pickle is a pickled cucumber (something to do with vinegar) and relish around here is diced up pickles with spices added.

What is a chutney?

You can pickle a lot of things, including many vegetables and fish, in a solution of brine and vinegar. The terms chutney and relish are often used interchangeably, but a chutney is usually considered to be an Indian-style relish made of fruits, such as mango, and certain spices, plus vinegar and sugar. Other relishes can include a variety of ingredients, not simply cucumber pickles. My mother makes one with corn, onions, and peppers.

This site offers a variety of chutney recipes.
https://www.bbcgoodfood.com/recipes/collection/pickles-jams-and-chutneys-recipes

Commonest chutneys in the UK are various mango ones, but people make green tomato chutney for themselves. One of my favourite chutneys is Mrs H.S. Ball's Original Recipe Chutney from South Africa - made from peaches and apricots. Yummmmmmm!!