Imagine you have a bunch of island countries. Each country needs to communicate with other countries for several affairs and to trade. A network connection is a route where boats transit back and forth between two said countries with people and things. The location of each island is encoded with a unique address, called an IP (Internet Protocol) address. The thing is, each country also has a huge, massive amount of different sea ports. A big amount of them. To be precise, 65536 different ones.
Each port number is associated with a service or a city that benefits from said sea traffic and expects boats. So to send a boat from one country to another, you need to send that boat from a specific port to a specific port in country (IP address). For example, port 80 is Website City in Google Land. You need to google something / send and receive boats with cargo (your search query). You have to send a boat from your own port 80 (Firefox Town) to Google Land (IP address of a Google server)'s own port 80 which is located in Website City.
Each network connection is a series of sea trips between cities.