A perfectly competitive market is a market where all competitors are very small businesses, supply prices are perfectly elastic, all goods sold are the same(no branding), abnormal profits can only be made in the short run
Perfect competition is a theoretical model so there is no real world example in our world an example I find easy is the milk market since the good is the same no matter the brand and the amount of branding is minimal and there is usually a good amount of competitors in a country