Cookies are tiny bits of data stored by an application on a user's computer through a respective web browser. They can be used to keep customized client data, sessions by the user on the application, or application data. We can set a deliberate duration time on our cookies from milliseconds to minutes, hours, days, and even much longer, depending on how long you want to persist the data.
We will have a look at one of the most important usages for cookies in collaboration with ASP.NET Core Identity when we deal with authentication later in Chapter 10, Securing ASP.NET Core 3 Applications.
We will deal with issues of security from Chapter 10, Securing ASP.NET Core 3 Applications, onward, but it is worth noting that cookies can present a vulnerability point to your application as they are often the targets of hackers. The best advice is to never store valuable information in your cookies but in tokens, which you use to locate your valuable data.