Aplenty means "in abundance," so if you are buying tons of chips and candy for your party, you can tell your friends there will be snacks aplenty.
When there's more than enough of something, it can be described as aplenty. There are dogs aplenty at the dogpark on a sunny day, and mashed potatoes aplenty on the table at Thanksgiving. This word is a postpositive adjective — like abreast or galore, aplenty always goes after the noun it's describing. It may sound a little old-fashioned, but there are occasions aplenty when it's the perfect word to use.