You can put the clock back by 40 odd years and just purchase an antenna and view the service from just your local TV stations. The daily service is free but you are limited by how far you are away from local transmitter and what hills and other obstacles are in the way. Maybe you would need to put the antenna on the roof to receive a satisfactory service.
However, today with good high speed internet and the right equipment you can reach worldwide sources and "stream" active and recorded stations and services. Some new televisions today may even have the ability to "stream" already installed, but if the TV is older, the cost of the equipment to enable "streaming" is relatively inexpensive and there are several choices.
A primary concern for streaming is the speed and reliability of your internet service and how it is available to your TV. The ideal connection is to use a wired, ethernet, connection which assumes that your internet modem and router are not very far away from the TV and so an ethernet cable can be easily run to the TV. In some cases this is not easy to do, so the other option is a WiFi connection. WiFi is a short range radio connection and is in fact the only connection possible with some of the streaming devices. If the internet speed is low or there is a large distance from the WiFi source to the streaming device buffering could result which means the TV show would keep pausing. Check out your WiFi by running https://www.speedtest.net/ or by watching a YouTube video by WiFi on a laptop or tablet that is positioned near the TV.
When it comes to what you want to watch there are thousands of options, some free, and many with a wide range of monthly costs. This means that one of your first tasks is to analyse what sort of TV you and your family want to watch and how much you want to pay. All payments are normally automatic and monthly by credit card. It is usually possible to easily cancel a particular service if you want to.