What is a request (request)?

A request is a message that a client sends to a server in order to get data or trigger some action.

The simplest way to put it: a request is the client's "ask" directed at the server.

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#Why a request is needed

Without a request, the server does nothing. The request is what:

• tells the server what the client needs
• triggers processing on the server
• starts the conversation between the client and the server

In client-server architecture, the client always speaks first.

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#What a request can contain

In its simple form, a request usually includes:

• what to do (for example: get data, send data, delete a resource)
• what to address (the resource's location on the server)
• additional data (login, password, parameters, the request body)

A real-life example:

"Give me the /profile page for user 123"

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#A practical example (HTTP)

The most familiar example is the HTTP request:

• a browser requests a web page
• a mobile app requests data from an API
• a program submits a form to the server

Even if a user just opens a website, a request is always happening underneath.

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#What happens after a request

1. The client sends a request
2. The server receives it
3. The server processes the request
4. The server builds a response
5. The client receives the response and uses it

A request always implies a response, even if that response is an error.

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#A real-life analogy

A request is like:

• an order in an online store
• a letter asking for something
• a question asked to a person

You ask first, and only then get an answer.

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#Short answer for an interview

Remember this phrasing:

A request is a message that a client sends to a server to get data or trigger a specific action. It initiates the interaction in client-server architecture.