AngularJS expressions are written inside double braces {{ expressions }} or inside a directive: ng-bind=”expression”. AngularJS expressions are like JavaScript expressions which can contain literals, operators, and variables.

In AngularJS, an expression is a JavaScript-like code snippet that is usually placed in bindings such as {{ expression }}. These expressions are evaluated against the scope object and can contain variables, functions, operators, and literals. They are used to bind data from the scope to the HTML, making it possible to display dynamic content in the view.

Here’s a breakdown of key aspects related to AngularJS expressions:

Evaluation: AngularJS expressions are evaluated in the context of the current scope, which means they have access to the data and functions defined within that scope.
Data Binding: Expressions are commonly used for data binding, where they interpolate values from the scope into the HTML. For example, {{ username }} might display the value of the username variable defined in the scope.
Filters: AngularJS expressions support filters, which are used for formatting data before displaying it. Filters can be chained together to perform multiple transformations on the data. For example, {{ amount | currency }} would format the amount variable as a currency.
No Control Flow or Looping: Unlike JavaScript code blocks, AngularJS expressions do not support control flow statements like if-else or loops. They are meant to be simple and primarily used for data binding.
Security: AngularJS expressions are evaluated in a sandboxed environment, which helps prevent execution of potentially harmful code (e.g., XSS attacks). However, developers should still be cautious about including user-generated content directly in expressions to mitigate security risks.

In summary, AngularJS expressions are a core feature that facilitates data binding and dynamic content rendering in AngularJS applications. They provide a convenient way to interact with data in the scope and present it in the view.