While the most important services that search engines provide is the indexing of content on the web, and providing this information through searches, they also provide some other services like web mail. This is different to email clients.
Web mail allows you to read emails that you receive and also reply or send new emails via the browser through a web mail interface. Many people use this type of service through their favourite search engine provider such as Gmail provided by Google, or Yahoo Mail.
In order to use this type of service which is usually offered for free, it means you need to open an account. Once you do, then you are given a dedicated web address which is what you access your mail through. In order to access your mail, you will have to log in using the password that you indicated when signing up for your web address.
Typical email client services are those that are provided by entities like Outlook or Thunderbird.
It really comes down to your personal preference, but more people are now turning to the email client services because they feel they are easier to use, and some feel that they are more secure. There are also some who get frustrated using the web mail services because they are too restricted.
With email clients, you are not using your browser to log into your email account, you are going through the software that is controlled by the email clients. One of the advantages about this type of email service is that you don’t need to be connected to the internet. Your emails sent and received are retained on your computer.
You may find that you have a email client already on your computer that you can access. This will likely be Outook Express or Outlook. You will have to use some basic set up to use this.