I don't have an article specifically for that.
You have a mailbox provided by someone - be it your ISP, Outlook.com, Gmail, Yahoo etc - and need to read the mail sent to your address.
Most email providers have web mail - you use a web browser to read your mail right from the mail server. You need to be connected to the internet to read your mail though.
Or you can use an email client installed on your computer to download your mail to your computer. Using an email client means you can read mail when you are not connected to the internet. You can also write an email, hit Send to add it to the outbox, but send it later. A mail client usually gives you more features and can make it easier to do things, like move mail to other folders.
It's not an either-or situation - where you always need to use a browser or an email client. If you are out and need to check mail from someone else's computer, you can still use a browser even if you use a mail client on your own computer.
Outlook software that comes with Office suite is the most well known mail client, but there are others - Windows 10 Mail, Thunderbird, eM client are just a few others - along with old, old clients like Windows Live Mail and Outlook Express. Can't forget Eudora - it was the best and most popular client before Outlook came along.