Sharkbite fittings are the easiest fittings for non-plumbers to use. They slide together without any need for glue. I have never had one fail. They can be used for multiple kinds of pipe: PEX, copper, etc.
Below are Amazon descriptions and links to three different kinds of fittings. These are affiliate links and I will get a commission if you go to Amazon and buy something.
Amazon products change a lot and I can possibly describe all the different kinds of fittings. These three links will open in a new window so you can look at pictures and descriptions of the different fittings. Some of the vendors have good descriptions of how to use the. In addition, you can see related products and product reviews to help you select the best fittings for your needs.
Notice the Tee above says "Sharkbite Style". It is cheaper and may work just as well as the branded products below. However, I have not tested that so buyer beware 🙂
This is a Sharkbite brand fitting. Plumbing part purchases are hard because there are so many variation is quality, design and dimensions. This is another example that will open in a new window so you can see a variety of choices.
With these three examples you should be able to quickly search through Amazon listings for the kind of parts you need, read the reviews, learn the vocabulary and buy with confidence. If you elect to buy at your local home improvement store you can be confident you will have the sizes and terms you need to find the right parts.