Thinking...
Okay, so the user is asking, "Can you explain what 2 + 2 does?" Hmm, that's a pretty
straightforward question, but maybe they're looking for more than just the answer. Let me
think.

First, I need to make sure I understand the question correctly. They might be a beginner
trying to grasp basic arithmetic, or maybe they're being a bit more abstract. Let me start
with the basics. In arithmetic, 2 + 2 is the sum of two numbers, each being 2. The result is
4. That's simple. But perhaps they want to know why it's 4? Like the underlying principles?

Let me recall how addition works. Addition is a binary operation that combines two numbers
into a total. So, 2 + 2 would be adding two units to another two units, resulting in four
units. But maybe they want a more formal explanation? Like using the Peano axioms or set
theory? That might be overkill, but it's worth considering.

Alternatively, maybe they're asking about the context in which 2 + 2 is used. For example,
in different number systems or contexts. Wait, in base 10, 2 + 2 is 4. But in some other
base, like base 3, 2 + 2 would be 11 (since 2 + 2 = 4 in decimal, which is 1*3 + 1). But the
user didn't specify the base, so probably base 10 is safe.

Another angle: in some contexts, like in George Orwell's "1984," 2 + 2 = 5 is a symbol of
totalitarianism. But the user is asking what 2 + 2 "does," not about its symbolic meaning.
Still, maybe they're curious about that? But the question seems more mathematical.

Wait, maybe they're confused about the operation itself? Like, what does the plus sign mean?
Addition is combining quantities. So, 2 + 2 is combining two quantities of 2. But maybe they
need a concrete example. Like, if you have two apples and someone gives you two more, you
have four apples total.

Or maybe they're thinking about programming? In some programming languages, 2 + 2 would
evaluate to 4. But in others, if the numbers are strings, it might concatenate them, like
"2" + "2" becomes "22". But the user didn't mention programming, so probably not that.

Alternatively, could there be a trick question here? Like, in some non-standard arithmetic
or a joke? But I don't think so. The user is probably seeking a straightforward answer.

Let me structure the answer. Start with the basic arithmetic answer. Then maybe explain the
concept of addition. Then perhaps mention different contexts if relevant. But since the user
is asking "what does it do," maybe focus on the operation's purpose. Addition is used to
find the total when combining two quantities. So, 2 + 2 is used to calculate the total when
you have two items and add two more.

Wait, maybe the user is a child learning math, so keeping it simple is key. Avoid complex
theories unless necessary. Also, check for any possible misunderstandings. For example, if
they think 2 + 2 is something else, like 5 in some contexts, but that's probably not the
case here.

In summary, the answer should state that 2 + 2 equals 4 in standard arithmetic, explain that
it's combining two quantities, and maybe touch on different contexts where the result might
differ. But since the question is direct, keep it concise.
...done thinking.

The expression **2 + 2** represents the **addition** of two numbers, each equal to 2. In
standard arithmetic, this operation calculates the total when you combine two quantities of
2. The result is:

**2 + 2 = 4**

### Breakdown:
1. **Addition**: The "+" symbol denotes the operation of adding two values.
2. **Result**: Combining 2 units with another 2 units gives a total of 4 units.
3. **Context**:
   - In **base 10 (decimal)**, this is straightforward: 2 + 2 = 4.
   - In **other contexts** (e.g., programming with strings), "2" + "2" might concatenate to
"22" instead of performing arithmetic. However, the question likely refers to numerical
addition.

### Why 4?
- **Basic Arithmetic**: Addition is defined as combining quantities. Two items plus two more
items equal four items.
- **Formal Systems**: In Peano axioms or set theory, 2 + 2 = 4 can be rigorously derived
using definitions of numbers and operations.
- **Real-World Example**: If you have 2 apples and receive 2 more, you now have 4 apples.

### Edge Cases:
- In **non-standard systems** (e.g., modulo arithmetic), 2 + 2 might not equal 4. For
example, in modulo 3, 2 + 2 = 1 (since 4 mod 3 = 1). But unless specified, the default is
standard arithmetic.

In summary, **2 + 2 = 4** in standard mathematics and is used to represent the combination
of two quantities into a total.