Both organic and paid results are types of search results on SERP shown on the basis of quality and relevance to the user query. Organic results are not paid to show up on SERP. It is very hard to rank high organically, and it requires SEO.
Paid results require bidding on keywords, and based on the Max CPC (cost per click) and quality score, they are positioned above the organic search results on SERP, and these are paid advertisements. The more you score, the less money you need to pay.